Introduction to PL/SQL

A Simple PL/SQL Block:
Each PL/SQL program consists of SQL and PL/SQL statements which form a
PL/SQL block.

A PL/SQL Block consists of three sections:

• The Declaration section (optional).
•  The Execution section (mandatory).
•  The Exception (or Error) Handling section (optional).

Declaration Section:
The Declaration section of a PL/SQL Block starts with the reserved keyword
DECLARE. This section is optional and is used to declare any placeholders like
variables, constants, records and cursors, which are used to manipulate data in the
execution section. Placeholders may be any of Variables, Constants and Records, which
stores data temporarily. Cursors are also declared in this section.
Execution Section:
The Execution section of a PL/SQL Block starts with the reserved keyword
BEGIN and ends with END. This is a mandatory section and is the section where the
program logic is written to perform any task. The programmatic constructs like loops,
conditional statement and SQL statements form the part of execution section.
Exception Section:
The Exception section of a PL/SQL Block starts with the reserved keyword
EXCEPTION. This section is optional. Any errors in the program can be handled in this
section, so that the PL/SQL Blocks terminates gracefully. If the PL/SQL Block contains
exceptions that cannot be handled, the Block terminates abruptly with errors.
Every statement in the above three sections must end with a semicolon ; .
PL/SQL blocks can be nested within other PL/SQL blocks. Comments can be used to
document code.