Building PL/SQL Blocks in Oracle 9i

This Week we will be learning about Creating PL/SQL Blocks which includes Declaration Section, Variables, Scope of Variables, Constants Records, Manipulating Data in PL/SQL and Using DML in PL/SQL .

PL/SQL is a procedural extension for Oracle’s Structured Query Language. PL/SQL is not a separate language rather a technology. Mean to say that you will not have a separate place or prompt for executing your PL/SQL programs. PL/SQL technology is like an engine that executes PL/SQL blocks and subprograms. This engine can be started in Oracle server or in application development tools such as Oracle Forms, Oracle Reports etc.

As shown in the above figure PL/SQL engine executes procedural statements and sends SQL part of statements to SQL statement processor in the Oracle server. PL/SQL combines the data manipulating power of SQL with the data processing power of procedural languages.

Block Structure of PL/SQL: PL/SQL is a block-structured language. i.e. Programs of PL/SQL contain logical blocks.

As shown in the Fig.2 a PL/SQL block has three parts.

1) Declaration: Necessary variables are declared in this section. (Optional)

2) Begin: This section contain executable statements of SQL and PL/SQL

3) Exception: Any error occurred while executing the statements in begin part can be handled in this part.

Variables and Constants: Variables are used to store query results. Forward references are not allowed. Hence you must first declare the variable and then use it.

Variables can have any SQL datatype, such as CHAR, DATE, NUMBER etc or any PL/SQL datatype like BOOLEAN, BINARY_INTEGER etc.

Declaring Variables: Variables are declared in DECLARE section of PL/SQL.

DECLARE
SNO NUMBER (3);
SNAME VARCHAR2 (15);
_ _ _
BEGIN

Assigning values to variables:

SNO NUMBER : = 1001; or SNAME := ‘JOHN’; etc

Following screen shot explain you how to write a simple PL/SQL program and execute it.

SET SERVEROUTPUT ON is a command used to access results from Oracle Server.
A PL/SQL program is terminated by a “ / “. DBMS_OUTPUT is a package and PUT_LINE is a procedure in it. You will learn more about procedures, functions and packages in the following sections of this tutorial.

Above program can also be written as a text file in Notepad editor and then executed as explained in the following screen shot.

SET SERVEROUTPUT ON is a command used to access results from Oracle Server.
A PL/SQL program is terminated by a “ / “. DBMS_OUTPUT is a package and PUT_LINE is a procedure in it. You will learn more about procedures, functions and packages in the following sections of this tutorial.

Above program can also be written as a text file in Notepad editor and then executed as explained in the following screen shot.

SET SERVEROUTPUT ON is a command used to access results from Oracle Server.
A PL/SQL program is terminated by a “ / “. DBMS_OUTPUT is a package and PUT_LINE is a procedure in it. You will learn more about procedures, functions and packages in the following sections of this tutorial.

Above program can also be written as a text file in Notepad editor and then executed as explained in the following screen shot.