Sybase

SYBASE SESSION 9-DOCUMENT

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INTRODUCTION TO OPEN CLIENT PROGRAMMING Chapter Includes: DB-Library Essential ct

Programming

pieces of a DB-library client

-Library Programming

Essential

Pieces Of a ct-Library Program

ODBC ODBC API

Interface

Conformance Levels

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Essential pieces of a DB-library client Each DB-Library program has a several essential pieces Entry

code

Opening

a connection to the server

A

message handler to process message from server

A

message handler to process message from DB-library

Exit

code

Entry Code: This

is the first step to initialize the library. In the introduction C registration is

more complex with the introduction of two callback functions. Registration

of the message and error handlers can occur at any time after

calling dbinit().

Opening a connection: After

initialization has done, it’s time to open a connection server. There are

25 connections by default Microsoft's

VBSQL object can manage up to 45 separate connection from a

single object by calling sqlsetmaxprocs(). When

opening a connection to a server a login record is first allocated with in

your local library. This

login records holds several pieces of information relevant to the

connection which must be set inside of your application

Two of the parameters are required Username Password

The message handler: Defining

a message handler is an essential part of even the smallest DBlibrary applications. The message handler deals with message from the server to the client, of in this case from sql server application. ___________________________________________________________________________________________________ Copyrights Reserved Page 3 of 8

The

message handler will be fired whenever a print statement is executed by the server or to report a problem to the client. Using

print is common inside stored procedure to pass user defined messages back to an application. When

the message handler is invoked, several parameters are passed in to it and the connection number the message number, the error state number, the security level, and the message context. Error Handler: The

error handler receives errors from DB-Library. These errors may report

that an sql server cannot be found, or the connection has been broken, or that not enough memory is available for a connection to be opened The

error handler like the message handler is passed a number of

parameters. These parameters are the connection number causing the error, the severity of the server, the error number, and the error description.

Exit Code: After

using the DB-library we have to shut down properly

Before It

exiting we have to make sure to call sqlwinExit().

is also good practice to call sqlExit() prior calling sqlwinExit().SqlExit()

closes all open connections and frees all allocated login structures.

Ct-Library Programming: Context: Every

ct-Lib application has a context. This context provides information

about the connection that belongs to the context. ___________________________________________________________________________________________________ Copyrights Reserved Page 4 of 8

Connections

can also have properties many of which are unique to a

connection and do not relate the context.

Allocating a connection structure: Connection

structures have certain properties that can be obtained from

sybase open client client/library The

function ct_con_props() takes six parameters

Constructing a command Batch: Once

a command structure has been allocated we have to use ct_command()

to put data in to the structure.

Submitting a batch: So It

to send the batch we have to call ct_send.

takes us a single argument and a pointer to the command to the command

structure

ODBC: ODBC

allows a single application to make a standard set of calls that are then

translated through the use of an ODBC driver, into statements on the target data base management system. It

is also possible to use SQL pass through simply to quote to the server, SQL

statements that are passed without being altered by the driver. Open

Database Connectivity (ODBC) provides a standard software API

method for using database management systems (DBMS). The

goal of ODBC is to make it possible to access any data from any

application, regardless of which database management system (DBMS) is handling the data. ___________________________________________________________________________________________________ Copyrights Reserved Page 5 of 8

ODBC

manages this by inserting a middle layer, called a database driver,

between an application and the DBMS. The

purpose of this layer is to translate the application's data queries into

commands that the DBMS understands. For this to work, both the application and the DBMS must be ODBC-compliant -- that is, the application must be capable of issuing ODBC commands and the DBMS must be capable of responding to them.

JDBC-ODBC bridges: A

Jdbc-Odbc bridge consists of a Jdbc driver that employs an ODBC driver to

connect to a target database. This

driver translates JDBC method calls into ODBC function calls.

Programmers usually use such a bridge when a particular database lacks a JDBC driver. An

ODBC-JDBC bridge consists of an Odbc driver, which uses the services of a

Jdbc driver to connect to a database.

ODBC Interface: ODBC

(Open Database Connectivity) is a standardized API that can be used to

access data stored in various database management systems (DBMSs). It

provides a product-neutral interface between front-end applications and

database servers, enabling a developer to write applications that are transportable between database servers from different vendors. The

Microsoft Open Database Connectivity (ODBC) interface is a C

programming language interface that makes it possible for applications to access data from a variety of database management systems (DBMSs). ODBC is a low-level, high-performance interface that is designed specifically for relational data stores. The

ODBC interface allows maximum interoperability—an application can

access data in diverse DBMSs through a single interface. Moreover, that ___________________________________________________________________________________________________ Copyrights Reserved Page 6 of 8

application will be independent of any DBMS from which it accesses data. Users of the application can add software components called drivers, which interface between an application and a specific DBMS.

ODBC Conformance Levels: ODBC defines two different conformance standards for drivers: API

conformance standard

SQL

conformance standard

Each conformance standard is made up of three levels. These levels help application and driver developers establish standard sets of functionality.

API Conformance Levels: The API conformance standard is made up of three levels: Core

API

Level

1 API

Level

2 API

Core API: A set of core functions that correspond to the functions in the X/Open SQL Access Group Call Level Interface specification. Level 1 API: Core API functionality plus all Level 1 functionality. Level 2 API: Core and Level 1 API functionality plus all Level 2 functionality.

ODBC API Functions: The

Connect ODBC drivers support all Core and Level 1 functions. In addition,

each driver supports a key set of the Level 2 functions. For a list of supported Level 2 functions by driver, refer to the "ODBC Conformance Levels" section for the database you are connecting to in the Connect ODBC Reference.

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1) What are the essential pieces of a DB-Library client? 2) Explain the essential pieces of a ct-Library Program 3) How do you construct a batch and submit a batch? 4) How do you allocate a Context structure. Connection Structure. Command structure. 5) What are the conformance levels in API? 6) By using VB how will you build a sample odbc application? 7)What is ODBC? Explain ODBC interface 8)How do you retrieve Object information?

Topics Covered: DB Library programming CT -Library Programming

Book for Reference Book: Sybase SQL Server 11 by Ray Rankins Jeffrey R. Garbus David Solomon

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