| 21. 1. 1. Block Structure |
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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: |
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[DECLARE
declaration_statements
]
BEGIN
executable_statements
[EXCEPTION
exception_handling_statements
]
END;
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- The declaration and exception blocks are optional.
- declaration_statements declares the variables subsequently used in the rest of the block.
- These variables are local to that block.
- Declarations are always placed at the start of the block.
- executable_statements are the actual executable statements for the block.
- executable_statements may include statements for performing tasks such as loops, conditional logic, and so on.
- exception_handling_statements are statements that handle any errors.
- Every statement is terminated by a semicolon (;).
- A block is terminated using the END keyword.
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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.
SQL>
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