Sql And Sql Plus Basics

INFORMATION TECHNOLOGY SERVICES

CCTS Software, Web Applications, and Training

Introduction to SQL for Oracle

NORTHERN ARIZONA UNIVERSITY

Introduction to SQL & SQL*PLUS

 Northern Arizona University Software, Web Applications, and Training Phone (520) 523-1511 • Fax (520) 523-7407

Table of Contents INTRODUCTION

MODULE

1

MODUL E

5

Intro to SQL and SQL*Plus

1

Creating Tables

33

Running SQL and SQL*Plus in Oracle

3

Dropping and Altering Tables

37

Getting Help

4

Creating Tables from Subqueries

38

Creating Demo Tables

38

Creating Views

39

MODULE

2

Running Simple Queries in SQL

5

Inserting, Updating & Deleting Records

41

Datatypes and Metadata

6

Committing Changes

42

Structuring Queries

8

Indexing Tables

42

Saving Queries & Running Saved-Queries 10 Operators

11

Comparison Operators

11

Arithmetic Operators

13

MODULE

Common Aggregate Functions

15

Creating Sequences

44

Creating Triggers

45

Using MS-Access as a Front End

46

SQL Loader

50

SQLPlus Worksheet

52

MODULE

3

Working with Dates & Date Functions

MODULE

19

4

GROUP BY Clause

25

ORDER BY Clause

28

HAVING Clause

30

Joining Tables

31

6

S O L U T I O N S

T O

E X E R C I S E S

A R E

I N

T H E

A P P E N D I X

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Introduction

Introduction

T

his course is designed to help you quickly learn the basics of SQL and SQL*PLUS queries. We will start from the beginning, assuming that you have no experience with SQL and take you through the steps. By the end of this course, you should be able to perform simple operations using SQL. This course has no prerequisites and you will soon discover that basic SQL is easy to learn and use. SQL*PLUS is proprietary to Oracle, so you need to have access to a computer running some version of Oracle8 or 9 to complete the exercises. Personal Oracle8 was used as the point of reference in creating this manual.

I T S

S O L U T I O N C E N T E R

Phone: (520) 523-1511 Fax: (520) 523-9259 http://www.nau.edu/its

About the Solution Center and the Software, Web Applications, & Training Teams

This manual was created for you by the ITS Software, Web Applications, & Training team. The Software, Web Applications, & Training (SWAT) team works with the Solution Center to provide our customers the best service possible. The mission of the Solution Center and the SWAT team is to maintain or increase the productivity of NAU staff and faculty by providing professional development and computing solutions from a central point of contact, and acting as an advocate for our customers in obtaining NAU computing support services. One of the goals of the SWAT team is to provide you with the training and training materials you need to improve your computing skills. Please feel free to contact us anytime with your computing or computer training questions.

II

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

ü 1

Course Objectives At the end of the course, students will be able to: 1. Identify SQL/SQL*PLUS statements. 2. Explain basic SQL/SQL*PLUS terms and concepts. 3. Use SQL command syntax to write simple queries. 4. Perform simple table joins. 5. Create and modify tables 6. Use sequences and triggers to generate autonumbers. 7. Effectively use MS-Access, SQL Loader, and SQL Plus Worksheet in Oracle-related tasks.

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Intro to SQL and SQL*PLUS

1

Module

SQL and SQL*PLUS.

S

QL is an acronym for “Structured Query Language”. SQL can be pronounced as “ess-cue-ell”, but many people refer to it as “sequel”. The paper, "A Relational Model of Data for Large Shared Data Banks," by Dr. E. F. Codd, was published in June 1970. Codd's model is now accepted as the definitive model for relational database management systems (RDBMS). SQL was developed by IBM to use Codd's model. In 1979, Relational Software, Inc. (now Oracle Corporation) introduced the first commercially available implementation of SQL. Today, SQL is accepted as the standard RDBMS language. By the late 1980’s there were over seventy-five SQL or SQL-like database management systems. Oracle SQL complies with industry-accepted standards. Oracle Corporation ensures future compliance with evolving SQL standards by actively involving key personnel in SQL standards committees. Industry-accepted committees are the American National Standards Institute (ANSI) and the International Standards Organization (ISO), which is affiliated with the International Electrotechnical Commission (IEC). Both ANSI and the ISO/IEC have accepted SQL as the standard language for relational databases. When a new SQL standard is simultaneously published by these organizations, the names of the standards conform to conventions used by the organization, but the standards are technically identical. The latest SQL standard is often called SQL92 (and sometimes SQL2). SQL92 defines four levels of compliance: Entry, Transitional, Intermediate, and Full. A conforming SQL implementation must support at least Entry SQL. Oracle8, Release 8.0, fully supports Entry SQL and has many features that conform to Transitional, Intermediate, or Full SQL.

1

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL provides commands for a variety of tasks, including: • • • • •

querying data inserting, updating, and deleting rows in a table creating, replacing, altering, and dropping objects controlling access to the database and its objects guaranteeing database consistency and integrity

SQL unifies all of the above tasks in one consistent language. All major relational database management systems support SQL, so you can transfer all skills you have gained with SQL from one database to another. In addition, all programs written in SQL are portable: they can often be moved from one database to another with very little modification. DDL and DML

SQL statements fall into two main categories: Data Definition Language (DDL) and Data Manipulation Language (DML). DDL commands create, change or remove database objects such as tables or users. Examples of DDL commands include: • • • • •

CREATE a database object such as a table DROP (delete) a database object ALTER a database object GRANT privileges on a database object REVOKE privileges on a database object

DML allows you to manipulate the contents of a database. You use DML to capture, insert, and delete data. Examples of DML commands include: • • • •

SELECT columns of data in a table INSERT rows of data in a table DELETE rows of data in a table UPDATE

SQL*PLUS

What is the difference between SQL and SQL*Plus? SQL is the standard database query language that all relational databases use to manipulate data. SQL*Plus is a programming environment where you can use SQL.

2

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL*Plus is usually thought of as a kind of interactive query tool and report writer. It uses SQL to get information from the Oracle data structure, and lets you create polished, well-formatted reports by giving you easy control over titles, column heading, subtotals and totals, formatting of numbers, dates, and text, and much more.

Running SQL*PLUS in Oracle To start SQL*Plus in Personal Oracle8, go to Start|Programs|Oracle for Windows NT (or Windows 95), and select SQL Plus 8.0. At the log on prompt, type scott for username and tiger for the password. Leave the host string blank.

You should see the following information:

You are now ready to begin entering SQL commands!

3

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

To start SQL*Plus on a mainframe or network, go to your operating system command line and type: SQLPLUS username|password.

Changing Your Password in NAUDEV You can also log into NAUDEV with your own account if one has been created for you. The password and username are most likely your userid. To test it log in with the following: Username: your_userid Password: your_userid Host: NAUDEV You should change your password once you have logged in to something more secure. Use the following SQL statement to change your password: SQL> alter user your_userid identified by new_password;

You should get a “user altered” message. The next time you log in, you will have to enter the new password.

Tip: In older versions of Oracle and in true client/server environments, you can access Help by typing “help” at the SQL prompt.

Getting Help To access help in Personal Oracle8, go to Start|Programs|Oracle for Windows NT (or Windows 95), and select Oracle Documentation. Your Web browser should open to the following page:

From here, you should be able to find your answer.

4

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Running Simple Queries in SQL

2

Module

Now that you have SQL up and running, let’s look at how to structure queries.

O

racle SQL*Plus comes with a demo database that contains several tables. Some of these tables already include data. We will use these tables for our exercises.

To see which tables are available, type in the following at the SQL prompt: and hit “enter”. SQL> select table_name from all_tables;

You should get this result: SQL> select table_name from all_tables; TABLE_NAME -----------------------------DUAL SYSTEM_PRIVILEGE_MAP TABLE_PRIVILEGE_MAP STMT_AUDIT_OPTION_MAP AUDIT_ACTIONS PSTUBTBL DEPT EMP BONUS SALGRADE USER_PROFILE LOCATION DEPARTMENT JOB EMPLOYEE SALARY_GRADE PRODUCT PRICE CUSTOMER SALES_ORDER ITEM 21 rows selected.

5

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

An alternative SQL statement that displays all available tables as the previous example did is: SQL> select * from tab;

Below is a list of all the tables that are available in the demo database. For this course, however, we will only use three: dept, emp, and salgrade. EMP Table EMPNO --------7369 7499 7521 7566 7654 7698 7782 7788 7839 7844 7876 7900 7902 7934

ENAME ---------SMITH ALLEN WARD JONES MARTIN BLAKE CLARK SCOTT KING TURNER ADAMS JAMES FORD MILLER

JOB MGR HIREDATE SAL COMM DEPTNO --------- --------- --------- --------- --------- --------CLERK 7902 17-DEC-80 800 20 SALESMAN 7698 20-FEB-81 1600 300 30 SALESMAN 7698 22-FEB-81 1250 500 30 MANAGER 7839 02-APR-81 2975 20 SALESMAN 7698 28-SEP-81 1250 1400 30 MANAGER 7839 01-MAY-81 2850 30 MANAGER 7839 09-JUN-81 2450 10 ANALYST 7566 19-APR-87 3000 20 PRESIDENT 17-NOV-81 5000 10 SALESMAN 7698 08-SEP-81 1500 0 30 CLERK 7788 23-MAY-87 1100 20 CLERK 7698 03-DEC-81 950 30 ANALYST 7566 03-DEC-81 3000 20 CLERK 7782 23-JAN-82 1300 10

DEPT Table DEPTNO --------10 20 30 40

DNAME -------------ACCOUNTING RESEARCH SALES OPERATIONS

LOC ------------NEW YORK DALLAS CHICAGO BOSTON

SALGRADE Table GRADE LOSAL HISAL --------- --------- --------1 700 1200 2 1201 1400 3 1401 2000 4 2001 3000 5 3001 9999

Datatypes and Metadata

The following datatypes can be used in Oracle: Datatype VARCHAR2(n)

Parameters n=1 to 2,000

Description Text string with variable length. Most

6

I N T R O D U C T I O N

T O

S Q L

A N D

NUMBER(p,s)

S Q L * P L U S

LONG

p=1 to 38, s=-84 to 127 or FLOAT none

DATE

none

RAW(n)

n=1 to 255

LONGRAW

none

CHAR(n)

n=1 to 255

commonly used datatype. For regular text. Number. p = precision (total number of Digits); s = scale (number of digits to the right of the decimal place). Text string with variable length. Maximum length is 2 gigabytes. Seldom used. For dates and times. Valid date range from January 1, 4712 BC to December 31, 4712 AD. Raw binary data of variable length. For files Like MS Word documents. Raw binary data of variable length. For graphics. Text string with fixed length. For short Codes, like state abbreviations.

Metadata

Metadata is the data about the data. It let’s us know how a table is structured. It is also referred to as the data dictionary.

To view the metadata of a table, use the DESCRIBE command. This will let you know exactly what the names of your columns are, as well as what types (datatypes) of information they contain. Let’s look at the metadata for the emp table. SQL> describe emp Name Null? ------------------------------- -------EMPNO NOT NULL ENAME JOB MGR HIREDATE SAL COMM DEPTNO

Type ---NUMBER(4) VARCHAR2(10) VARCHAR2(9) NUMBER(4) DATE NUMBER(7,2) NUMBER(7,2) NUMBER(2)

This information tells us that we have eight columns in the emp table called EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO. Of these columns, only one, EMPNO, must have something entered into it. We know this because of the NOT NULL listed next to it. We can also see what type of information must be entered into each column. For example, EMPNO must be a number not to exceed four digits. ENAME can be a maximum of ten letters, numbers, or symbols in any combination. SAL must be a number, not to exceed seven digits. Of those seven digits, two must be behind a decimal point. Therefore, you could not enter a number above 99,999.99. If you enter more than two decimal places, SQL will round up or down.

7

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Null and Not Null

As you may have noticed by now, each datatype can be set to allow either null or not null values. Null is defined as nothing. In Oracle, a zero, blank space, or any cha racter is a value, they are not null. Null means nothing at all. You can do queries for all records that have null, however. When a datatype is set to “not null”, it means that a value other than nothing has to be entered.

Structuring Queries Although SQL queries can become complicated, the basic structure is always the same. A SQL query has five main parts (clauses): SELECT FROM WHERE (optional) GROUP BY (optional) ORDER BY (optional) A sixth clause, HAVING, can also be discussed here. A sample query might look like: select last_name, address, salary from employees where salary > 20000 order by last_name

•

SELECT: Put the list of columns you want to see here. List all the columns, even if they are from several tables. Separate them with commas.

•

FROM: Put the table name here. If you have more than one table, list them all here, separated with commas.

•

WHERE (optional): Where some condition is true. Put comparisons, limits, and connections between tables here. List them with either AND or OR between each set. When left out, all rows are chosen.

•

GROUP BY (optional): Tells how you want data grouped or summarized. This is only needed for a query that summarizes data.

8

I N T R O D U C T I O N

Basic Query select column , column from table where clause group by clause order by clause having clause

T O

S Q L

A N D

S Q L * P L U S

•

ORDER BY (optional): List columns to use for sort order here. When left out, rows are returned in the order in which they are found in the table.

•

HAVING (optional): Similar to WHERE, but with some important distinctions that we’ll look at later.

SELECT specifies which column(s) in a table you want to see. FROM specifies the names of the table or tables in which the columns listed in the SELECT clause are located. If more than one table is listed, they should be separated by a comma. If you want to see all the columns, enter an asterisk. The following example shows how we would obtain all the information from the department table. SQL> select * from dept; DEPTNO --------10 20 30 40

DNAME -------------ACCOUNTING RESEARCH SALES OPERATIONS

LOC ------------NEW YORK DALLAS CHICAGO BOSTON

If we wanted to know just the department number and the location, we would have to select the specific columns. SQL> select deptno, loc 2 from dept; DEPTNO --------10 20 30 40

LOC ------------NEW YORK DALLAS CHICAGO BOSTON

Eliminating Duplicate Rows

Duplicate rows can be eliminated by using the DISTINCT keyword in the select clause. Notice the difference between the two select statements: SQL> select deptno from emp;

10 30 20 30 20 10

DEPTNO --------20 30 30 20 30 30 10 20

9

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL> select DISTINCT deptno from emp;

10 20 30

DEPTNO ---------

3

Exercise 2.1

1. Using SQL, display all the columns from the employee (emp) table. 2. Now display just the name (ename), position (job), and hire date (hiredate) of the employees. 3. Show the structure (metadata) of the DEPT table. 4. Select all data from the DEPT table. 5. Create a query to display unique (distinct ) jobs from the EMP table.

Saving and Running Queries Queries that will be run repeatedly can be saved as a file and then run later by typing in the name of the file. The default file extension is .sql. To save a file, write the query and execute it: SQL> select * 2 from emp 3 where ename='JAMES'; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO --------- ---------- --------- --------- --------- --------- --------- --------7900 JAMES CLERK 7698 03-DEC-81 950 30 SQL>

Then save it: SQL> save example Created file example SQL>

In Personal Oracle 8, the file is saved to the oracle8/BIN directory. Most likely, you will find it at C:/oracle8/BIN. There are two ways to run the saved query: SQL> start example EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO --------- ---------- --------- --------- --------- --------- --------- --------7900 JAMES CLERK 7698 03-DEC-81 950 30

or

10

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL> @example EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO --------- ---------- --------- --------- --------- --------- --------- --------7900 JAMES CLERK 7698 03-DEC-81 950 30

Either start or @ will run the saved query. You can also edit the saved query by entering edit followed by the filename: SQL> edit example

Once the file has been saved, you can later append more information to it by using the following command: SQL> save example append

Finally, you can replace the saved file by using the replace command with save: SQL> save example replace

Operators The WHERE Clause

The WHERE clause is the part of the SELECT clause that specifies the search conditions. These conditions determine which rows are retrieved. To set up these search conditions, we use operators. The system will search for rows of data that meet the conditions (qualifications) you specified by the operators. Remember that operator parameters are case sensitive. “Manager” is not the same as “manager”.

Comparison Operators

SQL provides a variety of operators and keywords for expressing search conditions. •

Comparison operators = > < >= <= != <>

SELECT EMP_ID FROM EMPLOYEES WHERE SALARY >= 50000;

equal to greater than less than greater than or equal to less than or equal to not equal to not equal to SELECT EMP_ID FROM EMPLOYEES WHERE POSITION = 'Manager';

11

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Notice that “Manager” is placed in single quotes in the where clause, while “50000” was not. Any character string, including dates, must be set off by single quotes, while numbers do not require this. •

Combinations or logical negations of conditions (AND, OR, NOT)

SELECT EMP_ID FROM EMPLOYEES WHERE SALARY > 40000 AND POSITION = 'Staff';

SELECT EMP_ID FROM EMPLOYEES WHERE SALARY < 40000 OR BENEFITS < 10000;

SELECT EMP_ID FROM EMPLOYEES WHERE POSITION = 'Manager' AND (SALARY > 50000 OR BENEFIT > 10000);

•

Ranges (BETWEEN and NOT BETWEEN)

SELECT EMP_ID FROM EMPLOYEES WHERE SALARY BETWEEN 30000 AND 50000;

•

SELECT EMP_ID FROM EMPLOYEES WHERE SALARY NOT BETWEEN 30000 AND 50000;

Lists (IN, NOT IN)

If you wanted to list all managers and staff: SELECT EMP_ID FROM EMPLOYEES WHERE POSITION IN ('Manager', 'Staff');

•

Unknown values (IS NULL and IS NOT NULL) example: where advance is null

•

Character matches (LIKE and NOT LIKE) example: where phone not like ‘415%’

Let’s say you wanted to see all people whose last names started with "L" in the EMPLOYEES table: SELECT EMPLOYEEIDNO FROM EMPLOYEESTATISTICSTABLE WHERE LASTNAME LIKE 'L%';

12

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

The percent sign (%) is used to represent any possible character (number, letter, or punctuation) or set of characters that might appear after the "L". To find those people with LastName's ending in "L", use '%L', or if you wanted the "L" in the middle of the word, try '%L%'. The “%” is a wildcard that can represent any number of characters. The character “_” can be used to match exactly one character. ename like ‘SMITH_’

would return SMITHE,

SMITHY, and SMITHS,

but not SMITHEY.

Arithmetic Operators

Arithmetic operators allow you to modify the way data is displayed, perform calculations, or look at what-if scenarios. Arithmetic operators can be used in any clause of a SQL statement except the FROM clause. Operator + * /

Description Add Subtract Multiply Divide

SQL> select ename, sal, sal+500 2 from emp; ENAME SAL SAL+500 ---------- --------- --------SMITH 800 1300 ALLEN 1600 2100 WARD 1250 1750 JONES 2975 3475 MARTIN 1250 1750 BLAKE 2850 3350 CLARK 2450 2950 SCOTT 3000 3500 KING 5000 5500 TURNER 1500 2000 ADAMS 1100 1600 JAMES 950 1450 FORD 3000 3500 MILLER 1300 1800 14 rows selected. Arithmetic Operator Precedence (* / + -)

•

Multiplication and division take priority over addition and subtraction.

•

Operators of the same priority are evaluated from left to right

•

Parentheses are used to force prioritized evaluation and to clarify statements

SQL> select ename, sal, 12*sal+200

2

13

from emp;

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

ENAME SAL 12*SAL+200 ---------- --------- ---------SMITH 800 9800 ALLEN 1600 19400 WARD 1250 15200 JONES 2975 35900 MARTIN 1250 15200 BLAKE 2850 34400 CLARK 2450 29600 SCOTT 3000 36200 KING 5000 60200 TURNER 1500 18200 ADAMS 1100 13400 JAMES 950 11600 FORD 3000 36200 MILLER 1300 15800 14 rows selected.

SQL> select ename, sal, 12*(sal+100) 2 from emp; ENAME SAL 12*(SAL+100) ---------- --------- -----------SMITH 800 10800 ALLEN 1600 20400 WARD 1250 16200 JONES 2975 36900 MARTIN 1250 16200 BLAKE 2850 35400 CLARK 2450 30600 SCOTT 3000 37200 KING 5000 61200 TURNER 1500 19200 ADAMS 1100 14400 JAMES 950 12600 FORD 3000 37200 MILLER 1300 16800 14 rows selected.

In the first example we multiplied the monthly salary by twelve and then added a onetime bonus of $200. In the following example, parentheses are used to raise the salary $100 per month and then multiply by twelve. Null Values

If a row lacks the data value for a particular column, that value is said to be null, or to contain null. A null value is not the same as zero or a space. Zero is a number, and a space is a character. NULL is absolutely nothing at all, but NULL can be used as a qualifier. Using Column Aliases

You may want to display the heading of a column as something other than “12*(SAL+100)”. This can be done by using a column alias. There are two ways to create an alias. One is to place the alias after “AS” in the select statement. The other way is to place the alias in quotation marks.

3

SQL> select mgr as manager, sal, comm 2 from emp;

SQL> select mgr, sal, comm"Commission" 2 from emp;

MANAGER SAL COMM --------- --------- --------7902 800 7698 1600 300

MGR SAL Commission --------- --------- ---------7902 800 7698 1600 300

Exercise 2.2

1. Create a query to display the name and salary of employees earning more than $2850. Save your SQL to statement to a file named q1.sql. Run your query. 2. Create a query to display the employee name and department number for employee number 7566.

14

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

3. Modify q1.sql to display the name and salary for all employees whose salary is not in the range of $1500 and $2850. Resave the SQL statement as q2.sql and run it. 4. List employees whose last names begin with “S”. 5. Find out how much Turner will make annually if we give her a $75 dollar a month raise. 6. Select all columns from the employee table, but cause the heading “ename” to be displayed as “Last Name”.

Common Aggregate Functions Oracle offers many functions for performing advanced and complicated manipulations with data. In this course, we will concentrate on some of the more common functions. These functions are called aggregate functions and they include SUM, AVG, COUNT, MAX, and MIN. Aggregates are functions you can use to get summary values. You apply aggregates to sets of rows: to all the rows in a table, to just those rows specified by a WHERE clause, or to groups of rows set up in the GROUP BY clause, (discussed in the next module). No matter how you structure the sets, you get a single value for each set of rows. All group functions except COUNT(*) ignore nulls. Aggregate Function

Result

SUM(expression)

The total of values in the numberic expression.

AVG (expression)

The average of values in the numeric expression.

COUNT(expression)

The number of non-null values in the expression.

COUNT(*)

The number of selected rows.

MAX(expression)

The highest value in the expression.

MIN(expression)

The lowest value in the expression.

SUM

This query provides the total amount of commissions:

15

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL> select sum(comm) 2 from emp; SUM(COMM) --------2200 AVG

Here we have the average of commissions paid, with a different heading: SQL> select avg(comm) "Average Commission" 2 from emp; Average Commission -----------------550

Let’s say that the commissions paid this month were indicative of commissions paid each month and we wanted to know what the average yearly commission might be: SQL> select avg(comm)*12 2 from emp; AVG(COMM)*12 -----------6600

COUNT

What if we wanted to know how many employees worked in the accounting department (dept. number 10): SQL> select count(deptno) 2 from emp 3 where deptno=10; COUNT(DEPTNO) ------------3

SQL> 2 3 4

select count(deptno) "Accounting Employees" from emp where deptno=10;

Accounting Employees -------------------3

COUNT(*)

The apparent similarity of COUNT and COUNT(*) can lead to confusion. However, the two are really not the same. COUNT takes an argument (a column or expression) and discovers all not-null occurrences of that argument, while COUNT(*) counts all rows, whether or not any particular column contains a null value. Let’s look at how each behaves in the following examples: SQL> select count(comm), count(*) 2 from emp; COUNT(COMM) COUNT(*) ----------- --------4 14

16

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

The results produced by the two functions are different because ten rows in the COMM column have null values. Note that the commission listed as “0” was counted by COUNT, because “0” is a value, and therefore is not null. You can use SUM and AVG with numeric columns only. MIN, MAX, COUNT, and COUNT(*) work with all types of data.

MAX

MAX provides the highest value in an expression. We can use max to find out who makes the highest salary: SQL> select max(sal) 2 from emp; MAX(SAL) --------5000 MIN

MIN provides the lowest value in an expression. MAX and MIN can be used for things other than the lowest or highest amount. For example we can use the following query to find out which employee has worked in the company the longest: SQL> select min(hiredate) 2 from emp; MIN(HIRED --------17-DEC-80 SQL> select ename, hiredate 2 from emp 3 where hiredate='17-DEC-80'; ENAME HIREDATE ---------- --------SMITH 17-DEC-80

While subqueries are beyond the scope of this course, I’ll point out that they exist and that one could have been used to obtain the same information in a single query using the following format: SQL> select ename, hiredate 2 from emp 3 where hiredate=(select min(hiredate) from emp); ENAME HIREDATE ---------- --------SMITH 17-DEC-80

Essentially, a subquery is nothing more than a query within a query

Using DISTINCT and ALL With Functions

DISTINCT can be used with a function to elimina te duplicate values. Look at the different results when SUM is used with and without DISTINCT. SQL> select sum(sal) 2 from emp;

SUM(SAL)

17

I N T R O D U C T I O N

T O

S Q L

A N D

--------29025

S Q L * P L U S

SQL> select sum(distinct sal) 2 from emp; SUM(DISTINCTSAL) ---------------24775

The difference in the two results comes from the fact that there are duplicate values of 1250 and 3000 in the SAL column.

DISTINCT

This option causes a group function to consider only distinct values the argument expression.

ALL

This option causes a group function to consider all values, including all duplicates.

For example, the DISTINCT average of 1, 1, 1, and 3 is 2; the ALL average is 1.5. If neither option is specified, the default is ALL.

3

Exercise 2.3

1. Display the highest, lowest, sum, and average salary of all employees. Label the columns Maximum, Minimum, Sum, and Average. 2. Write a query to count the number of employees. 3. Determine the number of clerks without listing them. Include the heading “Number of Clerks”.

18

I N T R O D U C T I O N

T O

S Q L

A N D

3

Module

S Q L * P L U S

Working with Dates and Date Functions Oracle stores dates in an internal numeric format, representing the century, year, month, day, hours, minutes, and seconds. The default display and input format for any date is DD-MON-YY. Valid Oracle dates are between January 1, 4712 BC and December 31, 9999 AD. SYSDATE

SYSDATE uses the computer’s operating system for the current date and time. SYSDATE can be thought of as a function whose result is always the current date and time. It can be regarded as a hidden column that is in every table. It is used in calculations that need to compare past or future dates/times with the current date or time. You can list the SYSDATE by itself by using the DUAL table, which is a small but useful Oracle table created for testing functions or doing quick calculations. Try it. SQL> select sysdate from dual;

Arithmetic with Dates

You can perform calculations on dates using arithmetic operators. Operation

Result

Description

date + number

date

Adds a number of days to a date

date - number

date

Subtracts a number of days from a date

date – date

number of days

Subtracts one date from another

date + number/24 date

Adds a number of hours to a date

19

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL> select ename, (sysdate-hiredate)/365.25 Years 2 from emp 3 where deptno = 10; ENAME ---------CLARK KING MILLER

YEARS --------17.561648 17.120854 16.937418

The preceding example displays the number of years that each employee in department 10 has worked. It subtracts the current date (SYSDATE) from the date on which the employee was hired and divides the result by 365.25 to calculate the number of years that a worker has been employed. Date Functions

Here is a list of a few date functions. We will not deal with them in this course, but I wanted to at least make you aware of them. Function

Description

months_between (date1, date2) months_between (‘01-sep-95’,’11-jan-94’)

Number of months between two dates

add_months (date, n) add_months (‘11-jan-94’,6)

Add calendar months to date

next_day (date, ‘char’) next_day (‘01-sep-95’,’Friday’)

Next date of the day specified

last_day (date) last_day (‘01-sep-95’)

Last day of the month

round (date [, ‘fmt’]) round (‘25-jul-95’,’month’) round (‘25-jul-95’,’year’) trunc (date [ , ‘fmt’]) trunc (‘25-jul-95’,’month’) trunc(‘25-jul-95’,’year’)

Round date

SQL> 2 3 4 5

Truncate date

select empno, hiredate, months_between (sysdate, hiredate) Tenure, add_months (hiredate, 6) Review, next_day (hiredate, 'friday'), last_day (hiredate) from emp where months_between (sysdate, hiredate) <200;

EMPNO --------7788 7876

HIREDATE TENURE REVIEW NEXT_DAY( --------- --------- --------- --------19-APR-87 140.40068 19-OCT-87 24-APR-87 23-MAY-87 139.27164 23-NOV-87 29-MAY-87

LAST_DAY( --------30-APR-87 31-MAY-87

TO_CHAR

to_char (date, ‘fmt’) Up to now, all date values were displayed in the DD-MON-YY format. The to_char function allows you to convert a date from this default format to one specified by you.

20

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL> select empno, to_char (hiredate, 'MM/YY') Month_Hired 2 from emp 3 where ename = 'KING'; EMPNO MONTH --------- ----7839 11/81

Here are some valid date formats: Element

Description

SCC or CC

Century; S prefixes BC date with -

Years in dates YYYY or SYYYY

Year; S prefixes BC date with -

YYY or YY or Y

Last 3, 2, or 1 digit(s) of year

Y,YYY

Year with comma in this position

SYEAR or YEAR

Year spelled out; S prefixes BC date with -

BC or AD

BC/AD indicator

B.C. or A.D.

BC/AD indicator with periods

Q

Quarter of year

MM

Month, two-digit value

MONTH

Full name of month

MON

Name of month, three-letter abbreviation

RM

Roman numeral month

WW or W

Week of year or month

DDD or DD or D

Day of year, month, or week

DAY

Full name of day

DY

Name of day; 3-letter abbreviation

21

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

The time portion of dates can also be formatted: Element

Description

AM or PM

Meridian indicator

A.M. or P.M.

Meridian indicator with periods

HH or HH12 or HH24

Hour of day or hour (1-12) or hour (0-23)

MI

Minute (0-59)

SS

Second (0-59)

SSSSS

Seconds past midnight (0-86399)

Finally, dates can formatted further in the following ways: Element

De

“of ” DD “of” MONTH

Quoted string is reproduce 23 of SEPTEMBER

TH

Ordinal number (DDTH for 4TH)

SP

Spelled-out number (DDSP for FOUR)

SPTH or THSP

Spelled-out ordinal numbers (DDSPTH for FOURTH)

SQL> select ename, to_char (hiredate, 'Ddspth "of" Month YYYY HH:MI:SSAM') 2 Hiredate 3 from emp; ENAME ---------SMITH ALLEN WARD JONES MARTIN BLAKE CLARK SCOTT KING TURNER ADAMS JAMES

HIREDATE ------------------------------------------Seventeenth of December 1980 12:00:00AM Twentieth of February 1981 12:00:00AM Twenty-Second of February 1981 12:00:00AM Second of April 1981 12:00:00AM Twenty-Eighth of September 1981 12:00:00AM First of May 1981 12:00:00AM Ninth of June 1981 12:00:00AM Nineteenth of April 1987 12:00:00AM Seventeenth of November 1981 12:00:00AM Eighth of September 1981 12:00:00AM Twenty-Third of May 1987 12:00:00AM Third of December 1981 12:00:00AM

22

I N T R O D U C T I O N

T O

S Q L

FORD MILLER

A N D

S Q L * P L U S

Third of December 1981 12:00:00AM Twenty-Third of January 1982 12:00:00AM

14 rows selected.

To_char can be used with numbers in the same way. It converts a number to a character datatype. to_char (number, ‘fmt’) Element Description

Example of

9s 99999

Result

9

Numeric position (number determine display width)

1234

0

Display leading zeros

099999

001234

$

Floating dollar sign

$999999

$1234

.

Decimal point in position specified

9999999.99

1234.00

,

Comma in position specified

999,999

1,234

MI

Minux signs to right (negative values)

999999MI

1234-

PR

Parenthesize negative numbers

999999PR

<1234>

EEEE

Scientific notation (format must specify 99.999EEEE four Es)

1.234E+03

V

Multiply by 10 n times (n = no. of 9s after 9999V99 V)

123400

SQL> select to_char (sal, '$99,999') Salary 2 from emp 3 where ename = 'TURNER'; SALARY -------$1,500

TO_DATE and TO_NUMBER Functions

These two functions can be used to convert a character string to either a number or a date. The format model you choose will be based on the previously demonstrated format elements.

23

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

to_number (char) to_date (char[ , ‘fmt’]) Example: Display the names and hire dates of all the employees who joined on February 22, 1981. SQL> select ename, hiredate 2 from emp 3 where hiredate = to_date ('February 22, 1981', 'Month dd, YYYY'); ENAME HIREDATE ---------- --------WARD 22-FEB-81

Birthday Trick

Use the following query to see what day you were born on. Substitute the date with your own birth date. Be careful to type everything exactly. SQL> select to_char(to_date('23-sep-63'), 'Day') "Born on" from dual; Born on --------Monday

3

Exercise 3.1

1. Write a query to display the current date. 2. Now write a query to display the current date in a different format, such as the “4th of July”. Display it first as a numeral and then run a second query that spells it out. Label the heading “Today’s Date”. 3. How many months has Turner been employed? 4. Display the name of every employee who was hired in 1982.

24

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Organizing & Grouping Data

4

Module

We’ll look at the GROUP BY, ORDER BY, and HAVING clauses in this module, as well as how to query data from multiple tables.

T

he GROUP BY and ORDER BY clauses can be used to organize your query results, so that they display the data in a more meaningful way. The HAVING clause works in a manner similar to the WHERE clause, but with some important differences.

GROUP BY

The GROUP BY clause is usually used with an aggregate function such as SUM or AVG. GROUP BY doesn’t really have much use without aggregate functions. GROUP BY divides a table into sets, while aggregate functions produce summary values for each set. Until now, all aggregate functions have treated the table as one large group of information. At times, you need to divide the table of information into smaller groups. This can be done by using the GROUP BY clause. You can use the GROUP BY clause to divide the rows in a table into groups. You can then use the group functions to return summary information for each group. Guidelines: • If you include a group function in a SELECT clause, you cannot select individual results as well unless the individual column appears in the GROUP BY clause. You will receive an error message if you fail to include the column list. • Using a WHERE clause, you can exclude rows before dividing them into groups. • You must include the columns in the GROUP BY clause. • You cannot use a column alias in the GROUP BY clause. • By default, rows are sorted by ascending order of the columns included in the GROUP BY list. You can override this by using the ORDER BY clause

25

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL> select deptno, avg(sal) 2 from emp 3 group by deptno; DEPTNO --------10 20 30

AVG(SAL) --------2916.6667 2175 1566.6667

When using the GROUP BY clause, make sure that all columns in the SELECT list that are not in the group functions are included in the GROUP BY clause. The above example displays the department number and the average salary for each department. Here is how the SELECT statement above, containing a GROUP BY clause is evaluated.

• • •

• The SELECT clause specifies the columns to be retrieved: − Department number column in the EMP table − The average of all the salaries in the group you specified in the GROUP BY clause The FROM clause specifies the tables that the database must access: the EMP table. The WHERE clause specifies the rows to be retrieved. Since there is no WHERE clause, by default all rows are retrieved. The GROUP BY clause specifies how the rows should by grouped. The rows are being grouped by department number, so the AVG function that is being applied to the salary column will calculate the average salary for each department.

SQL> select avg(sal) 2 from emp 3 group by deptno; AVG(SAL) --------2916.6667 2175 1566.6667

You can also use the ORDER BY clause to rearrange the query results. SQL> select deptno, avg(sal) 2 from emp 3 group by deptno; DEPTNO --------10 20 30

SQL> 2 3 4

AVG(SAL) --------2916.6667 2175 1566.6667

select deptno, avg(sal) from emp group by deptno order by avg(sal);

DEPTNO --------30 20 10

26

AVG(SAL) --------1566.6667 2175 2916.6667

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Grouping by More Than One Column

Sometimes there is a need to see results for groups within a group. The table below shows a report that displays the total salary being paid to each job title, within each department. The EMP table is grouped first by department number and then within that grouping it is grouped by job title. For example, the two clerks in department 20 are grouped together and a single result (total salary) is produced for all salesmen within the group. SQL> select deptno, job, sum(sal) 2 from emp 3 group by deptno, job; DEPTNO --------10 10 10 20 20 20 30 30 30

JOB SUM(SAL) --------- --------CLERK 1300 MANAGER 2450 PRESIDENT 5000 ANALYST 6000 CLERK 1900 MANAGER 2975 CLERK 950 MANAGER 2850 SALESMAN 5600

9 rows selected.

You can return summary results for groups and subgroups by listing more than one GROUP BY column. You can determine the default sort order of the results by the order of the columns in the GROUP BY clause. Here is how the SELECT statement above, containing a GROUP BY clause, is evaluated: •

• •

The SELECT clause specifies the column to be retrieved: − Department number in the EMP table − Job title in the EMP table − The sum of all the salaries in the group you specified in the GROUP BY clause. The FROM clause specifies the tables that the database must access: the EMP table. The GROUP BY clause specifies how you must group the rows: − First, the rows are grouped by department number. − Second, within the department number groups, the rows are grouped by job title.

So the SUM function is being applied to the salary column for all job titles within each department number group.

27

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Here is another example of the GROUP BY clause: SQL> select deptno, count(ename) 2 from emp 3 group by deptno; DEPTNO COUNT(ENAME) --------- -----------10 3 20 5 30 6

You cannot use the WHERE clause to restrict groups. Note the following error which results from a misuse of the WHERE clause SQL> select deptno, avg(sal) 2 from emp 3 where avg(sal) > 2000 4 group by deptno; where avg(sal) > 2000 * ERROR at line 3: ORA-00934: group function is not allowed here

You can correct the above error by using the HAVING clause to restrict groups. SQL> 2 3 4

select deptno, avg(sal) from emp group by deptno having avg(sal) > 2000;

DEPTNO AVG(SAL) --------- --------10 2916.6667 20 2175

We’ll discuss the HAVING clause more in depth shortly. Exercise 4.1

1. Display the minimum, maximum, sum, and average salary for each job type (analyst, clerk, manager, president, salesman). 2. Write a query to display the number of people with the same job.

ORDER BY

The ORDER BY clause arranges your query results by one or more columns. The default order is ascending. If you want the list to be sorted in descending order, you have to use DESC in the ORDER BY clause.

28

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

SQL> select empno, ename 2 from emp 3 order by ename;

SQL> select empno, ename 2 from emp 3 order by ename desc;

EMPNO --------7876 7499 7698 7782 7902 7900 7566 7839 7654 7934 7788 7369 7844 7521

EMPNO --------7521 7844 7369 7788 7934 7654 7839 7566 7900 7902 7782 7698 7499 7876

ENAME ---------ADAMS ALLEN BLAKE CLARK FORD JAMES JONES KING MARTIN MILLER SCOTT SMITH TURNER WARD

14 rows selected.

ENAME ---------WARD TURNER SMITH SCOTT MILLER MARTIN KING JONES JAMES FORD CLARK BLAKE ALLEN ADAMS

14 rows selected.

You can also sort by more than one column. When you use more than one column in the ORDER BY clause, sorts are nested ( that is, ordered by job first and then by ename within each job category. You can have as many levels of sorts as you like. The following example sorts the query result first by job title and then by last name. SQL> select job, ename, empno 2 from emp 3 order by job, ename; JOB --------ANALYST ANALYST CLERK CLERK CLERK CLERK MANAGER MANAGER MANAGER PRESIDENT SALESMAN SALESMAN SALESMAN SALESMAN

ENAME EMPNO ---------- --------FORD 7902 SCOTT 7788 ADAMS 7876 JAMES 7900 MILLER 7934 SMITH 7369 BLAKE 7698 CLARK 7782 JONES 7566 KING 7839 ALLEN 7499 MARTIN 7654 TURNER 7844 WARD 7521

14 rows selected.

You could also add DESC to one or both of the columns in the ORDER BY clause to reverse sort the query result. Exercise 4.2

1. Display the employee name, job and start date of employees hired between February 20, 1981, and May 1, 1981. Order the query in ascending order of start date.

29

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

2. Display the employee name and department number of all employees in departments 10 and 30 in alphabetical order by name. 3. Display the name, salary, and commission for all employees who earn commissions. Sort data in descending order of salary and commissions.

The HAVING Clause

In its most common usage, the HAVING clause is a WHERE clause for groups. Just as WHERE limits rows, HAVING limits groups. Most of the time, you use HAVING with GROUP BY. When there are aggregates in the select list of a query, WHERE clause conditions apply to the aggregates, while HAVING conditions apply to the query as a whole, after you’ve calculated the aggregates and set up the groups. SQL> 2 3 4

select deptno from emp group by deptno having max(sal) > 2900;

DEPTNO --------10 20

The following example displays the job title and total monthly salary for each job title with a total payroll exceeding $5000. The example excludes salesmen and sorts the list by the total monthly salary. SQL> 2 3 4 5 6

select job, sum(sal) payroll from emp where job not like 'SALES%' group by job having sum(sal)>5000 order by sum(sal);

JOB PAYROLL --------- --------ANALYST 6000 MANAGER 8275

Exercise 4.3

1. Display the manager number and the salary of the lowest paid employee for that manager. Exclude anyone where the manager id is not known. Exclude any groups where the minimum salary is less than $1000. Sort the output in descending order of salary.

30

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Joining Tables In a database that has been designed properly, one table may not give you all the information that you need. When this happens, you may need to query more than one table at the same time using a join operation. The join operation lets you retrieve and manipulate data from more than one table in a single SELECT statement. In most cases, you specify joins in the WHERE clause of a SELECT statement. The format of a join statement looks like this: Select From Where

table.column, table.column table1, table2 table1.column1=table2.column2

To perform a simple or inner join, you need to join the two tables together by using a column that is found in both tables, usually as a primary key in one table and a foreign key in the other. Let’s look at a join involving the EMP and DEPT tables. SQL> select emp.empno, emp.ename, emp.deptno, dept.deptno, dept.loc 2 from emp, dept 3 where emp.deptno=dept.deptno; EMPNO --------7369 7499 7521 7566 7654 7698 7782 7788 7839 7844 7876 7900 7902 7934

ENAME DEPTNO DEPTNO LOC ---------- --------- --------- ------------SMITH 20 20 DALLAS ALLEN 30 30 CHICAGO WARD 30 30 CHICAGO JONES 20 20 DALLAS MARTIN 30 30 CHICAGO BLAKE 30 30 CHICAGO CLARK 10 10 NEW YORK SCOTT 20 20 DALLAS KING 10 10 NEW YORK TURNER 30 30 CHICAGO ADAMS 20 20 DALLAS JAMES 30 30 CHICAGO FORD 20 20 DALLAS MILLER 10 10 NEW YORK

14 rows selected.

31

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

You can cut down on the typing by using table aliases in the SELECT statement. A table alias is defined in the FROM clause after the actual table name. SQL> select e.empno, e.ename, e.deptno, d.deptno, d.loc 2 from emp e, dept d 3 where e.deptno=d.deptno; EMPNO --------7369 7499 7521 7566 7654 7698 7782 7788 7839 7844 7876 7900 7902 7934

ENAME DEPTNO DEPTNO LOC ---------- --------- --------- ------------SMITH 20 20 DALLAS ALLEN 30 30 CHICAGO WARD 30 30 CHICAGO JONES 20 20 DALLAS MARTIN 30 30 CHICAGO BLAKE 30 30 CHICAGO CLARK 10 10 NEW YORK SCOTT 20 20 DALLAS KING 10 10 NEW YORK TURNER 30 30 CHICAGO ADAMS 20 20 DALLAS JAMES 30 30 CHICAGO FORD 20 20 DALLAS MILLER 10 10 NEW YORK

14 rows selected.

Sometimes you may need to join more than one table. This is done in the following manner (This table is an example only. It will not work with your practice tables) SQL> 2 3 4

select e.name, e.emp_id, d.deptno, d.manager, p.project_id from employee e, department d, projects p where e.deptno=d.deptno and d.manager=p.manager;

Exercise 4.4

1. Write a query to display the employee name, department number, and department name for all employees. List the results alphabetically by name. 2. Write a query to display the employee name, department name, commission, and location of all employees who earn a commission. 3. Write a query to display the name, job, department number, and department name for all employees who work in Dallas.

32

I N T R O D U C T I O N

T O

S Q L

A N D

5

Module

S Q L * P L U S

Creating and Working with Tables

N

ow that you know how to pull data out of tables that were created for you, you probably want to know how to create your own tables, drop (delete) them, and alter them as necessary. This module will give you the knowledge to create your own tables and fields and then alter or modify them after you have created them. Naming Conventions

There are certain restrictions on names you give to tables and columns. Table and column names: • • • • •

Must begin with a letter Can be 1-30 characters long Must contain only A-Z, a-z, 0-9,_,$, and # Must not duplicate the name of another object owned by the same user Must not be Oracle Server reserved words

To create a table, you need to specify the name of the table and then specify its fields and the datatypes of those fields. Here is an example: SQL> 2 3 4

create table table_name ( id number(4), name varchar2(20), city varchar2(20));

This will create a table called “table_name” with three fields: an ID field which can take up to four numbers and a name and a city field which can each hold up to twenty alphanumeric characters. Not null constraints

One problem with the table is that users can leave fields blank if they want to. You may or may not want to allow this. If you want to force the user to enter data, you can do this by using the words “not null” when creating the table as demonstrated by the following example:

33

I N T R O D U C T I O N

T O

S Q L

SQL> 2 3 4

A N D

S Q L * P L U S

create table table_name ( id number(4), name varchar2(20) not null, city varchar2(20));

A not null constraint has now been placed on the “name” field. This means that a record cannot be inserted without a value being placed in this field. The following constraints are available in Oracle: 1. 2. 3. 4.

Not Null –specifies that a column may not contain a null value Unique – Specifies a column whose values must be unique for all rows Primary Key – Uniquely identifies each row of the table Foreign Key – Establishes and enforces a foreign key relationship between the column and a column of the referenced table 5. Check – Specifies a condition that must be true Unique Key Constraint

A unique key constraint requires that every value in a column be unique. No two rows of a table can have duplicate values. SQL> 2 3 4

create table table_name ( id number(4), name varchar2(20) unique, city varchar2(20));

The unique constraint will allow more than one null value, but it would prevent you from entering John Smith twice. It would not prevent you from entering John Smith and JOHN SMITH, however, because Oracle is case sensitive. Primary Key Constraint

A primary key constraint creates a primary key for the table. Only one primary key can be created for each table. The primary key ensures that the value in each row is unique and prevents null values from being entered. SQL> 2 3 4

create table table_name ( id number(4) primary key, name varchar2(20), city varchar2(20));

Foreign Key Constraint

A foreign key constraint is used to relate tables. The foreign key is defined in the child table, and the table containing the referenced column is the parent table. The foreign key is created with a combination of the following keywords: FOREIGN KEY is used to define the column in the child table at the table constraint level. REFERENCES identifies the table and column in the parent table. ON DELETE CASCADE indicates that when a row in the parent table is deleted, the dependent rows in any child tables will also be deleted. Without the ON DELETE CASCADE option, the row in the parent table cannot be deleted if it is referenced in the child table.

34

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Let’s create the parent table first: SQL> create table parent_table ( 2 id number(2) primary key, 3 city varchar2(20));

Now let’s create the child table and create a foreign key to reference the “id” column in the parent table. SQL> 2 3 4 5 6

create table child_table ( child_id number(2) primary key, name varchar2(20), id number(2) not null, constraint childtable_id_fk FOREIGN KEY (id) REFERENCES parent_table (id));

Now enter some information into your tables: SQL> insert into parent_table values (01, 'FLAGSTAFF'); SQL> insert into parent_table values (02, 'PHOENIX'); SQL> insert into child_table values (10, 'JOHN SMITH', 01);

This enters data into your tables and relates the John Smith record to Flagstaff by virtue of the foreign key. Now try to delete the Flagstaff record from the parent table: SQL> delete from parent_table where id=01;

What happened? Let’s do an alter table command to add “ON DELETE CASCADE” to the foreign key constraint. First drop (delete) the old constraint. SQL> alter table child_table 2 drop constraint CHILDTABLE_ID_FK;

Now add a new constraint that contains the “ON DELETE CASCADE” clause to the child table: SQL> 2 3 4

alter table child_table add constraint childtable_id_fk Foreign key(id) references parent_table(id) ON DELETE CASCADE;

Try to drop the Flagstaff record now and see what happens now that we’ve added the ON DELETE CASCADE clause. SQL> delete from parent_table where id=01;

Check the child table and note that the dependent record has also been deleted. SQL> select * from child_table

35

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Check Constraint

Check constraints define a condition that each row must satisfy. A check constraint that makes sure that the id column does not contain four-digit numbers below 1000 or above 5000 can be created with the following statement: SQL> 2 3 4 5

create table table_name ( id number(4) constraint tablename_id_ck check (id between 999 and 5001), name varchar2(20) not null, city varchar2(20));

Note that you are actually creating a constraint with its own name, “tablename_id_ck”. You can check for all uppercase letters in the name column by using this constraint: SQL> 2 3 4 5

create table table_name ( id number(4), name varchar2(20) not null constraint tablename_name_ck check (name=upper(name)), city varchar2(20));

The previous statement will not allow nulls or lower case letters to be entered into the name column, but it will allow numbers and certain symbols. Of course another way to ensure that you only get capital letters would be to convert lowercase letters automatically when they are inserted, which we will cover in the next module. If you want to allow only capital letters: SQL> 2 3 4 5

create table table_name ( id number(4), name varchar2(20) not null constraint tablename_name_ck check (name between ‘A’ and ‘Z’), city varchar2(20));

Constraints can also be used on dates, including sysdate, and can be used in simple logic statements. check (start_date < sysdate and (end_date > sysdate or end_date is null))); check ((job = ‘SALESMAN’ and comm IS NOT NULL) or job != ‘SALESMAN’ and comm IS NULL))

Viewing Constraints on a Table

Constraints set on a table can be viewed by executing the following statement. Substitute the name of the table you want to view for CHILD_TABLE and be sure to use uppercase letters. SQL> SELECT constraint_name, constraint_type, search_condition 2 FROM user_constraints 3 where table_name = ‘CHILD_TABLE’;

36

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Setting Default Values on a Column

You can also set default values in a table when you create it. This might be useful in a situation where a value to be entered is frequently the same. In our example, let’s say that most people who are entered into the table will most likely live in Flagstaff. You may likely want to use Flagstaff as a default value to save some typing. SQL> 2 3 4

create table clients ( id number(2), name varchar2(20), city varchar2(20) default ‘FLAGSTAFF’);

Now try inserting data in the first two columns only and then select it: SQL> SQL>

insert into clients (id,name) values (10, 'JOHN SMITH'); select * from clients;

You should see that Flagstaff has automatically been entered in the city column. You should be able to do the same thing with dates, including the sysdate function. SQL> 2 3 4

create table employees ( id number(2), name varchar2(20), hiredate date default sysdate);

Dropping and Altering Tables There are times when you will want to drop (delete) tables that have been created. This is very easy to and can be done with this simple statement: SQL> drop table table_name

In other cases, you may simply want to modify the structure of a table. This can be done with the Alter Table statement. The alter table statement is used to add, modify or delete columns, add or remove constraints as we saw above, define a default value on a new column, and even to rename a table. To demonstrate how to add a column, let’s first create the new table: SQL> create table clients ( 2 id number(2), 3 name varchar2(20);

Now let’s add the city column using the alter table statement: SQL> alter table clients 2 ADD (city varchar2(20));

37

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

You can also use alter table to modify columns. You can change a column’s datatype, size, default value, and NOT NULL column constraint. Let’s modify the name column to be thirty spaces instead of twenty. SQL> alter table clients 2 MODIFY (name varchar2(30));

A feature that first showed up with Oracle8 is the ability to drop a column as well. The statement to do this is: SQL> alter table clients 2 drop (name);

The table can also be renamed by executing the following statement: SQL> rename clients to client_table

Creating Tables from Subqueries An easy way to create new tables from exisiting data is to create one using a subquery. The following query will create a new table with selected columns from the “emp” table. We’ll call it “employees”. SQL> create table employees 2 as 3 select * from emp;

This is a handy feature. You can create tables from very sophisticated queries and joins that provide only the data you need. You can also do this with views, which we will look at in module seven.

Creating and Dropping Demo Tables Oracle has several practice tables that we have been using throughout this course. You should recognize them as emp, dept, bonus, salgrade, and dummy. There are two scripts that are installed with the Oracle client that allows you to add and drop these tables repeatedly. This is useful if you want to play with the tables and change data, but then be able to set everything back to how it was originally. The two scripts (files) are demobld.sql and demodrop.sql. Demobld will drop and create the demo tables, while demodrop simply drops them. You do not need to drop the tables using demodrop.sql if you just want to erase your changes and start with a fresh set of demo tables you only need to execute demobld. Demobld.sql and demodrop.sql can be located under the current Northern Arizona University install at c:\Oracle/ORA81/sqlplus/demo/demobld.sql.

38

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

To run this script from the SQL*Plus tool, simply type in @c:\Oracle/ORA81/sqlplus/demo/demobld.sql and press the enter key.

Creating Views You may create tables that contain data that you don’t want to be made available to certain people or groups. Rather than create new tables with redundant data, you can create a “view” of the table which only presents the data fields that you want to make available. A view is set up with certain privileges for users. A view can also be configured to control how data is manipulated in the table. For example, you may want to set it up so that users can only see the data and not be allowed to update it. To create the view, you specify the name and then use a select statement: SQL> create view employeeVU 2 as select empno, ename, job 3 from employees 4 where deptno=20; View created.

Now check the view: SQL> select * from employeeVU; EMPNO ENAME JOB ---------- ---------7369 7566 7788 7876 7902

SMITH JONES SCOTT ADAMS FORD

CLERK MANAGER ANALYST CLERK ANALYST

To drop a view: SQL> drop view employeeVU; View dropped.

You can rename the column names when you create your view in the following manner: SQL> create view employeeVU 2 as select empno ID, 3 ename NAME, job TITLE 4 from employees 5 where deptno=20; View created.

39

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Now test it: SQL> select * from employeeVU; EMPNO ENAME JOB ---------- ---------7369 7566 7788 7876 7902

SMITH JONES SCOTT ADAMS FORD

CLERK MANAGER ANALYST CLERK ANALYST

Creating a view from multiple tables

An especially handy feature of views is that you can create what looks and acts like a table from multiple tables and functions. You cannot update data in this type of view, however. SQL> create view emp_stats_vu 2 (name, minsal, maxsal, avgsal) 3 as select d.dname, min(e.sal), 4 max(e.sal), avg(e.sal) 5 from emp e, dept d 6 where e.deptno=d.deptno 7 group by d.dname; View created.

Now test it: SQL> select * from emp_stats_vu; NAME MINSAL MAXSAL AVGSAL -------------- ---------- ---------- ---------ACCOUNTING 1300 5000 2916.66667 RESEARCH 800 3000 2175 SALES 950 2850 1557.14286

This is just a superficial overview of views. There are many rules and commands that you need to be aware of before using a view in a production environment. For more information consult the comprehensive Oracle complete reference guide or an online resource such as http://www.oracle.com or http://otn.oracle.com.

40

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Inserting Records Now that you know how to create and manage tables and views, let’s look at how to insert data into your tables and manage it once it’s there. It’s actually a pretty simple and straight-forward process. To insert a record, use the following statement: SQL> insert into employees 2 values (8888,’ROBERTS’,’ACTRESS’,7839,’01-FEB-02’,10000,0,50);

Remember that varchar2 and date datatypes need to be enclosed in quotes, while number datatypes do not. If you only want to insert data in certain fields, then you must identify the fields by name. SQL> insert into employees (empno,ename) 2 values (8888,’SUTHERLAND’);

Updating Records To update a record, use the following statement:: SQL> update employees 2 set job=’ACTOR’,mgr=7839,hiredate=’01-FEB-02’,sal=10000,deptno=50 3 where ename=’SUTHERLAND’;

You can update as many or as few of the columns as you like.

Deleting Records To delete a record, use the following statement: SQL> delete from employees 3 where ename=’SUTHERLAND’;

41

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Make sure that you use a where clause with the delete statement, or you may delete the entire contents of the table! If you do this by accident, you can use the rollback function to correct it, but you must do it before you commit. We will look at the commit function in the following section. SQL> delete from employees; 17 rows deleted. SQL> rollback; Rollback complete.

Committing Changes After making changes to records, you need to issue a “commit” command to make the changes permanent. Oracle will make them permanent if you exit from the SQL*Plus tool, but it is a good idea to get in the habit of committing after important changes. This becomes very important if you are designing dynamic web pages that present data from your Oracle tables. The changes appear to have been made in SQL*Plus, but they will not show up in your web pages until you have issued a commit command. Remember this and save yourself potentially hours of frustration if you present data on the web. SQL> commit; Commit complete.

As we saw in the last section, you can also issue a rollback command and undo all of the changes up to the point where you last issued a commit command. SQL> rollback; Rollback complete.

Creating an Index If you have a large table in which only a small percentage of records are expected to be returned at any one time, then you will probably want to create an index to speed query searches. An index is an independent object, separate from the table it indexes. It speeds up the retrieval of data by using a pointer and can reduce disk input/output by using a rapid path access method. Since indexes are independent of the tables, they can be dropped at any time without affecting the data in the tables or the tables themselves. You probably do not want to use indexes on a table that is updated frequently as it may slow down inserts or updates. There are two types of indexes. An implicit index is created automatically when you define a primary key or unique constraint on a table. An explicit constraint is created when you manually execute a create index statement as shown below.

42

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

To create an index: SQL> create index employees_empno_idx 2 on employees(empno); Index created.

You can view the indexes you created by using the following: SQL> select ic.index_name, ic.column_name, 2 ic.column_position col_pos, ix.uniqueness 3 from user_indexes ix, user_ind_columns ic 4 where ic.index_name = ix.index_name 5 and ic.table_name = 'employees';

To drop the index: SQL> drop index employees_empno_idx;

43

I N T R O D U C T I O N

T O

S Q L

A N D

6

Module

S Q L * P L U S

Other Tips

T

he next step is to learn how to use sequences and triggers to allow for automatic numbering and to cause things to happen when an event occurs. We’ll also look at how to schedule jobs to make things happen to your data and tables at pre -determined times.

Sequences

Many tables need unique numbers to serve as primary key values. A sequence generator can be used to automatically assign unique numbers to a row. When combined with a trigger, a sequence can create the equivalent of an Access database autonumber, which automatically creates a new number each time a record is inserted into a table. Sequences are typically used to generate primary numbers. Sequence numbers are independent of tables, so one sequence can be used on multiple tables. To create a sequence, follow this general syntax: create sequence sequence_name increment by n start with n no cache; The “increment by” clause can be left out if you want it to increase by one number at a time, which is the default. The “start with” clause can also be left out if you want the sequence number to begin at one, but it can be useful in a case where you need the sequence number to start at a value like 1000. “No cache” is important if you are using the sequence to create sequential numbers and it’s important that you don’t have any missing values. Oracle tends to pre -allocate 20 values per day. If your table only inserts three records the first day, it will assign the numbers 1, 2, and 3. If you didn’t specify “no cache” when you created the sequence, your sequence value will start at 21 the following day. We are going to create a sequence to generate an autonumber. The sequence will also need a trigger, which we will create in the next section. To generate the sequence type:

44

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Create sequence autonumber start with 1 nocache; You should get a “Sequence created” message if it was successful. To drop the sequence, use “drop sequence sequence_name” If you are embedding an SQL insert statement in something like Active Server Pages, you can create an autonumber that will be initiated by the code itself, rather than an event trigger in the table. You can do it this way: Insert into records_table values (autonumber.nextval, ‘SMITH’) “Autonumber” is the name of the sequence and “nextval” tells the sequence to give you the next value available. “SMITH” is just data in the second column. As mentioned, this works fine if you can count on a dynamic page or other code to trigger the sequence event. In other cases where a front end such as Microsoft Access is being used to insert data, a sequence combined with a trigger is probably the best situation. The trigger allows the sequence to fire internally when a record is inserted, without relying on external code, such as Visual Basic in an Active Server Page. Triggers

Here’s how the trigger is created. Give it the name of the owner, in this case employee is the tablename. ID is the name of the field where the autoincrement will be. “number(5)” specifies the datatype and number of digits. SQL> create or replace trigger triggername_bef_ins_row 2 before insert on employee referencing 3 OLD old NEW new for each row 4 declare 5 Emp_ID number(5); 6 begin 7 select autonumber.nextval into Emp_ID from dual; 8 :new.Emp_ID := Emp_ID; 9 END; 10 / Trigger created. This creates a trigger that will automatically place a sequential number in whichever column specified. This works like an autonumber in Access and allow access to be used as a front end to Oracle in situations where a primary key are similar automatically generated unique value is necessary.

45

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Using Miicrosoft Access as a Front End to Oracle

Not everyone wants to learn SQL nor do they want to write a lengthy SQL statement just to insert a record. Microsoft Access provides a convenient, GUI-based front end for these users. This can be especially useful in situations where a department is storing data in one of ITS’s Oracle databases, but someone is responsible for maintaining the data who has no strong technical aptitude and wants to avoid SQL at all costs. To set up Access as a front end, first create your tables in Oracle using SQL*Plus and then follow these steps. Open a blank Access database.

Now go to the File menu and select Get External Data > Link Tables. In the “Link” dialog box that pops up, find “Files of Type: Microsoft Access” and scroll to the bottom to change “Microsoft Access” to “ODBC Databases”. Click OK.

46

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Select the “Machine Data Source” tab and click on the “New” button.

Select System Data Source and click the Next button.

47

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Click on the “Microsoft ODBC for Oracle” driver and click the next button. Note that this is different from the “Oracle ODBC Driver” which may also be listed in your choices. The Oracle ODBC Driver is not recommended because of some anomalies that have been noticed in the NAU env ironment. Click on the Next button and then click “Finish”. Now fill in the box that should pop up.

“Naudev_tables” can be any name you want to give your ODBC connection. A description can also be entered if useful. Put your Oracle username in and then most likely NAUDEV or ITSDEV for the Server name, depending on where your tables are located. Click OK. The new ODBC name should now be highlighted. Simply click OK and then enter the Oracle password that the DBA’s assigned to you. (Don’t forget to change this password shortly after they assign it.) See page ??? if you forgot how to do this. You should now see this box:

Find your username and the tables that are located in your space. Choose one or more tables and click OK. If you can’t find any tables above a certain letter, it means that you probably used the “Oracle ODBC Driver” instead of the “Microsoft ODBC for Oracle” drive. If so, go back, delete the ODBC connection and re -create it using Microsoft ODBC for Oracle.

48

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Access will probably prompt you for a Unique Record Identifier. This is only important for Access and does not change anything on the Oracle side. You should choose something however or you probably will not be able to enter any data through Access, only view it. Click the OK button.

Your link to the Oracle table is now complete. You will notice that the table icon is different than what is usually seen in Access. (It is a globe with an arrow.) This represents a linked table. The good news is that once you have this link, it can be treated as any other table in Access. Queries, forms, and modules can be written in Access that actually run against the Oracle tables. As mentioned above, this can be a very powerful tool, especially when non-technical personnel are expected to manage the data. Plus it gives you the security of having your data stored and backed up on ITS professionally-managed databases.

49

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Module Six – Lab (Suggested solutions are in the back of the manual.) 1. Create a new table called lab_one and add several columns, including one called unique_id and make it a primary key with an identifiable name. 2. Using an SQL insert statement, enter one or two records into the new table. 3. Now create a sequence, named something like “autonumber”, which will be used to create an autonumber in the unique_id field. 4. Since we will use Access as a front end, you will also want to create a trigger to cause the sequence to insert a value when a new record is inserted. 5. Now create an Access front end to your new table. Once it is set up, try to insert a couple of records through the GUI interface. Which tool do you prefer, SQL*Plus or Access?

SQL Loader So how do you get large numbers of records into your tables without having to enter each record by hand? There is a tool called SQL Loader that will let you enter data from a delimited text file. The hard part is setting up the control file, but once you have done this, the records can be loaded in a few seconds to a few minutes depending on the quantity of data. Whole books have been written on SQL Loader, most notably one by O’Reilly, which is devoted entirely to the intricacies of this command line tool. First of all, you need to do a search for the tool to make sure you have it. Look for “sqlldr.exe”. It should be in a path like c:\ORACLE\ora81\bin. SQL*Loader reads files and places the data from those files in an Oracle database based on the instructions it receives from a control file. The control file describes the data being loaded and tells Oracle where to place it. The SQL loader tool isn’t included in the NAU download install, so you need to get it form a complete install from the CD or ask your friendly neighborhood SWAT team member for it.

50

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

1. First we need to create a table to hold the data: Create table class_info (idno number(4), course_no number(3), day_of_class varchar2(20), Building varchar2(50), Seats_remaining number(2), instructor varchar2(50)) storage (initial 1m next 100k pctincrease 0 maxextents unlimited); The last few lines dealing with “storage” are sometimes needed to avoid a “max extents” error that occurs sometimes depending on the amount of data you are trying to load. If you get a max extents error, you need to add this storage clause when creating the table. The DBA’s at NAU have se the default max extents to ten and the clause changes that to allow for loading of large amounts of data. 2. Now create the control file and store it as “class_info.ctl”. (Note the “replace” in the second line. This option wipes out existing data. Use “append” if you want to add to existing data.): load data infile class_info.txt replace into table class_info fields terminated by ‘,’ optionally enclosed by ‘”’ trailing nullcolls (idno, course_no, day_of_class, building, seats_remaining, instructor)

Chyfo at http://www.ispirer.com is a nice little tool which will creat all of the necessary files and scripts for you when migrating data from various database to Oracle. It is a command line tool and you still have to have a pretty good understanding of how things work to use it effectively, however. Don’t forget about the O’Reilly book, which is a great resource if you want to get serious about using SQL loader and tools like Chyfo. Your instructor will tell you where to get the data file, called “class_info.txt”. Place it in the same directory as the control file. I usually create a directory at the root, “C:\loaddata”, for example, to keep the path short and simple. Now open a command prompt and enter the following:

51

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Sqlldr username/password@naudev control=c:\loaddata/class_info.ctl (You can set this up as a batch file.) SQL Loader creates a log that explains how data was loaded and whether anything went wrong. It is usually dumped in c:\documents and settings/yourusername.

SQL*Plus Worksheet Another tool that you can install from the ITS dba website is the SQL*Plus Worksheet. The worksheet works pretty much the same way as the SQL*Plus tool, but it provides a slightly more intuitive graphical interface for running queries and has two panes: one for the SQL queries and other commands and a second for the output. It’s worth taking a look at. You will probably find it by going to the Start menu and going to Oracle > Database Administration > SQLPlus Worksheet

52

I N T R O D U C T I O N

T O

S Q L

A N D

S Q L * P L U S

Solutions

Solutions to Exercises Exercise 2.1

1. SQL> select * 2 from emp; EMPNO --------7369 7499 7521 7566 7654 7698 7782 7788 7839 7844 7876 7900 7902 7934

ENAME ---------SMITH ALLEN WARD JONES MARTIN BLAKE CLARK SCOTT KING TURNER ADAMS JAMES FORD MILLER

JOB MGR HIREDATE SAL COMM DEPTNO --------- --------- --------- --------- --------- --------CLERK 7902 17-DEC-80 800 20 SALESMAN 7698 20-FEB-81 1600 300 30 SALESMAN 7698 22-FEB-81 1250 500 30 MANAGER 7839 02-APR-81 2975 20 SALESMAN 7698 28-SEP-81 1250 1400 30 MANAGER 7839 01-MAY-81 2850 30 MANAGER 7839 09-JUN-81 2450 10 ANALYST 7566 19-APR-87 3000 20 PRESIDENT 17-NOV-81 5000 10 SALESMAN 7698 08-SEP-81 1500 0 30 CLERK 7788 23-MAY-87 1100 20 CLERK 7698 03-DEC-81 950 30 ANALYST 7566 03-DEC-81 3000 20 CLERK 7782 23-JAN-82 1300 10

14 rows selected.

2. SQL> select ename, job, hiredate 2 from emp; ENAME ---------SMITH ALLEN WARD JONES MARTIN BLAKE CLARK SCOTT KING TURNER ADAMS JAMES FORD MILLER

JOB --------CLERK SALESMAN SALESMAN MANAGER SALESMAN MANAGER MANAGER ANALYST PRESIDENT SALESMAN CLERK CLERK ANALYST CLERK

HIREDATE --------17-DEC-80 20-FEB-81 22-FEB-81 02-APR-81 28-SEP-81 01-MAY-81 09-JUN-81 19-APR-87 17-NOV-81 08-SEP-81 23-MAY-87 03-DEC-81 03-DEC-81 23-JAN-82

14 rows selected.

i

3. SQL> describe dept Name Null? ------------------------------- -------DEPTNO NOT NULL DNAME LOC

Type ---NUMBER(2) VARCHAR2(14) VARCHAR2(13)

4. SQL> select * 2 from dept; DEPTNO --------10 20 30 40

DNAME -------------ACCOUNTING RESEARCH SALES OPERATIONS

LOC ------------NEW YORK DALLAS CHICAGO BOSTON

5. SQL> select distinct job 2 from emp; JOB --------ANALYST CLERK MANAGER PRESIDENT SALESMAN

Exercise 2.2

1. SQL> select ename, sal 2 from emp 3 where sal > 2850; ENAME SAL ---------- --------JONES 2975 SCOTT 3000 KING 5000 FORD 3000

2. SQL> select ename, deptno 2 from emp 3 where empno=7566; ENAME DEPTNO ---------- --------JONES 20

3.

ii

SQL> select ename, sal 2 from emp 3 where sal not between 1500 and 2850; ENAME SAL ---------- --------SMITH 800 WARD 1250 JONES 2975 MARTIN 1250 SCOTT 3000 KING 5000 ADAMS 1100 JAMES 950 FORD 3000 MILLER 1300 10 rows selected.

4. SQL> select ename 2 from emp 3 where ename like 'S%'; ENAME ---------SMITH SCOTT

5. SQL> select ename, 12*sal "Old Salary", 12*(sal+75)"New Salary" 2 from emp 3 where ename='TURNER'; ENAME Old Salary New Salary ---------- ---------- ---------TURNER 18000 18900

6. (Do this query first to find out what columns are in the table) SQL> describe emp Name Null? ------------------------------- -------EMPNO NOT NULL ENAME JOB MGR HIREDATE SAL COMM DEPTNO

Type ---NUMBER(4) VARCHAR2(10) VARCHAR2(9) NUMBER(4) DATE NUMBER(7,2) NUMBER(7,2) NUMBER(2)

Then run the query on the following page.

iii

SQL> select empno, ename as "Last Name", job, mgr, hiredate, 2 sal, comm, deptno 3 from emp; EMPNO --------7369 7499 7521 7566 7654 7698 7782 7788 7839 7844 7876 7900 7902 7934

Last Name ---------SMITH ALLEN WARD JONES MARTIN BLAKE CLARK SCOTT KING TURNER ADAMS JAMES FORD MILLER

JOB MGR HIREDATE SAL COMM DEPTNO --------- --------- --------- --------- --------- --------CLERK 7902 17-DEC-80 800 20 SALESMAN 7698 20-FEB-81 1600 300 30 SALESMAN 7698 22-FEB-81 1250 500 30 MANAGER 7839 02-APR-81 2975 20 SALESMAN 7698 28-SEP-81 1250 1400 30 MANAGER 7839 01-MAY-81 2850 30 MANAGER 7839 09-JUN-81 2450 10 ANALYST 7566 19-APR-87 3000 20 PRESIDENT 17-NOV-81 5000 10 SALESMAN 7698 08-SEP-81 1500 0 30 CLERK 7788 23-MAY-87 1100 20 CLERK 7698 03-DEC-81 950 30 ANALYST 7566 03-DEC-81 3000 20 CLERK 7782 23-JAN-82 1300 10

14 rows selected.

Exercise 2.3

1. SQL> select max(sal) "Maximum", min(sal) "Minimum", 2 sum(sal) "Sum", avg(sal) "Average" 3 from emp; Maximum Minimum Sum Average --------- --------- --------- --------5000 800 29025 2073.2143

2. SQL> select count(empno) 2 from emp; COUNT(EMPNO) -----------14

3. SQL> select count(job) "Number of Clerks" 2 from emp 3 where job='CLERK'; Number of Clerks ---------------4

iv

Exercise 3.1

1. SQL> select sysdate 2 from dual; SYSDATE --------25-JAN-99

2. SQL> select to_char (sysdate, 'ddth "of" Month') "Today's Date" 2 from dual; Today's Date ----------------25th of January SQL> select to_char (sysdate, 'ddspth "of" Month') "Today's Date" 2 from dual; Today's Date --------------------------twenty-fifth of January

3. SQL> select ename, months_between (sysdate, hiredate) 2 from emp 3 where ename='TURNER'; ENAME MONTHS_BETWEEN(SYSDATE,HIREDATE) ---------- -------------------------------TURNER 208.56175

4. SQL> select ename, hiredate 2 from emp 3 where hiredate between '01-JAN-82' and '31-DEC-82'; ENAME HIREDATE ---------- --------MILLER 23-JAN-82

or

v

SQL> select ename, hiredate 2 from emp 3 where hiredate like '%-%-82'; ENAME HIREDATE ---------- --------MILLER 23-JAN-82

Exercise 4.1

1. SQL> select job, min(sal), max(sal), sum(sal), avg(sal) 2 from emp 3 group by job; JOB MIN(SAL) MAX(SAL) SUM(SAL) AVG(SAL) --------- --------- --------- --------- --------ANALYST 3000 3000 6000 3000 CLERK 800 1300 4150 1037.5 MANAGER 2450 2975 8275 2758.3333 PRESIDENT 5000 5000 5000 5000 SALESMAN 1250 1600 5600 1400

2. SQL> select job, count(job) 2 from emp 3 group by job; JOB COUNT(JOB) --------- ---------ANALYST 2 CLERK 4 MANAGER 3 PRESIDENT 1 SALESMAN 4

Exercise 4.2

1. SQL> 2 3 4

select ename, job, hiredate from emp where hiredate between '20-FEB-81' and '01-MAY-81' order by hiredate;

ENAME ---------ALLEN WARD JONES BLAKE

JOB --------SALESMAN SALESMAN MANAGER MANAGER

HIREDATE --------20-FEB-81 22-FEB-81 02-APR-81 01-MAY-81

vi

2. SQL> 2 3 4

select ename, deptno from emp where deptno=10 or deptno=30 order by deptno, ename;

ENAME DEPTNO ---------- --------CLARK 10 KING 10 MILLER 10 ALLEN 30 BLAKE 30 JAMES 30 MARTIN 30 TURNER 30 WARD 30

3. SQL> 2 3 4

select ename, sal, comm from emp where comm is not null order by sal desc, comm desc;

ENAME SAL COMM ---------- --------- --------ALLEN 1600 300 TURNER 1500 0 MARTIN 1250 1400 WARD 1250 500

Exercise 4.3

1. SQL> 2 3 4 5 6

select mgr, min(sal) from emp group by mgr having mgr is not null and min(sal) > 1000 order by min(sal) desc;

MGR MIN(SAL) --------- --------7566 3000 7839 2450 7782 1300 7788 1100

Exercise 4.4

1. SQL> 2 3 4

select emp.ename, emp.deptno, dept.dname from emp, dept where emp.deptno=dept.deptno order by ename;

or SQL> select e.ename, e.deptno, d.dname 2 from emp e, dept d 3 where e.deptno=d.deptno

vii

4

order by ename;

ENAME DEPTNO DNAME ---------- --------- -------------ADAMS 20 RESEARCH ALLEN 30 SALES BLAKE 30 SALES CLARK 10 ACCOUNTING FORD 20 RESEARCH JAMES 30 SALES JONES 20 RESEARCH KING 10 ACCOUNTING MARTIN 30 SALES MILLER 10 ACCOUNTING SCOTT 20 RESEARCH SMITH 20 RESEARCH TURNER 30 SALES WARD 30 SALES

2. SQL> 2 3 4

select e.ename, e.deptno, e.comm, d.loc from emp e, dept d where e.deptno=d.deptno and comm is not null;

ENAME DEPTNO COMM LOC ---------- --------- --------- ------------ALLEN 30 300 CHICAGO WARD 30 500 CHICAGO MARTIN 30 1400 CHICAGO TURNER 30 0 CHICAGO

3. SQL> 2 3 4

select e.ename, e.job, e.deptno, d.dname from emp e, dept d where e.deptno=d.deptno and loc='DALLAS';

ENAME ---------SMITH JONES SCOTT ADAMS FORD

JOB DEPTNO DNAME --------- --------- -------------CLERK 20 RESEARCH MANAGER 20 RESEARCH ANALYST 20 RESEARCH CLERK 20 RESEARCH ANALYST 20 RESEARCH

viii