Select_query.docx

SELECT QUERY - is used to fetch data from the MySQL database. - is an incredibly powerful tool that enables you to transform data into information. - is used to retrieve records from one or more tables in MySQL. The syntax for the SELECT statement is: SELECT column list FROM tableName WHERE conditions;

•

The SELECT statement allows you to get particular columns of information in the output of the query

•

FROM selects the table(s) that the query is going to use to produce the resulting information

•

WHERE is a TRUE/FALSE resulting clause Fig 1.1 SELECT ALL without WHERE condition.

Using the syntax SELECT * FROM [TableName]; will display all the values inserted inside the said table.

1|Page

Fig 1.2 SELECT Specific Column without WHERE condition.

Using the syntax SELECT [ColumnName,ColumnName] FROM [TableName]; will display the values of the columns listed on the select query.

Fig 1.3 SELECT All Column with WHERE condition.

Using the syntax SELECT *FROM [TableName] WHERE [condition]; will display the values of the rows that results TRUE to the WHERE Condition of the statement. The WHERE clause is used to filter records. It is used to extract only those records that fulfill a specified condition.

2|Page

The following operators can be used in the WHERE clause: SYMBOL

Meaning

=

Equal to

<

Less than

<=

Less than or equal to

>

Greater than

>=

Greater than or equal to

<> Or !=

Not equal to

The WHERE clause can also be combined with AND, OR, and NOT operators. The AND and OR operators are used to filter records based on more than one condition: 

The AND operator displays a record if all the conditions separated by AND is TRUE.

Fig 2.1 SELECT All Column with WHERE condition Combined with AND logical Operator.

3|Page

Fig 2.2 SELECT All Column with WHERE condition Combined with AND logical Operator.

Both Figure 2.1 and Figure 2.2 show a SELECT ALL statement with WHERE clause combined with And Logical Operator the only difference is in Figure 2.1 both conditions in WHERE clause returns TRUE that’s why it displays an output of 1 row while in Figure 2.2 the condition returns only one true answer.



The OR operator displays a record if any of the conditions separated by OR is TRUE.

Fig 2.3 SELECT All Column with WHERE condition Combined with OR logical Operator.

4|Page



The NOT operator displays a record if the condition(s) is NOT TRUE.

Fig 2.4 SELECT All Column with WHERE condition Combined with NOT logical Operator.

SQL Wildcard Characters A wildcard character is used to substitute any other character(s) in a string. Wildcard characters are used with the SQL LIKE operator. The LIKE operator is used in a WHERE clause to search for a specified pattern in a column. There are two wildcards used in conjunction with the LIKE operator: 

% - The percent sign represents zero, one, or multiple characters

5|Page



_ - The underscore represents a single character

Fig 2.4 SELECT All Column with WHERE condition Combined with LIKE Special Operator. The query states that it should display or view all details in the table which has Name that starts with any character and ends with ‘ead’.

6|Page