Block Structure : Introduction « PL SQL Data Types « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. PL SQL Data Types
3. Introduction

You typically use PL/SQL to add business logic to the database.

PL/SQL programs are divided up into structures known as blocks.

Each block containing PL/SQL and SQL statements.

A typical PL/SQL block has the following structure:

[DECLARE
  declaration_statements
]
BEGIN
  executable_statements
[EXCEPTION
  exception_handling_statements
]
END;

1. The declaration and exception blocks are optional.
2. declaration_statements declares the variables subsequently used in the rest of the block.
3. These variables are local to that block.
4. Declarations are always placed at the start of the block.
5. executable_statements are the actual executable statements for the block.
6. executable_statements may include statements for performing tasks such as loops, conditional logic, and so on.
7. exception_handling_statements are statements that handle any errors.
8. Every statement is terminated by a semicolon (;).
9. A block is terminated using the END keyword.

DECLARE        
  2    width INTEGER;
  3    height INTEGER := 2;
  4    area INTEGER;
  5  BEGIN
  6    area := 6;
  7    width := area / height;
  8    DBMS_OUTPUT.PUT_LINE('width = ' || width);
  9  EXCEPTION
 10    WHEN ZERO_DIVIDE THEN
 11      DBMS_OUTPUT.PUT_LINE('Division by zero');
 12  END;
 13  /
width = 3

PL/SQL procedure successfully completed.

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