CASE Statement

The simple CASE statement evaluates a single expression and compares it to several potential values.

The searched CASE statement evaluates multiple Boolean expressions and chooses the first one whose value is TRUE.

Topics

Syntax

simple_case_statement ::=

Description of the illustration simple_case_statement.eps

searched_case_statement ::=

Description of the illustration searched_case_statement.eps

(boolean_expression ::=, statement ::=)

Semantics

simple_case_statement

selector

Expression whose value is evaluated once and used to select one of several alternatives. selector can have any PL/SQL data type except BLOB, BFILE, or a user-defined type.

WHEN selector_value THEN statement

selector_value can be an expression of any PL/SQL type except BLOB, BFILE, or a user-defined type.

The selector_values are evaluated sequentially. If the value of a selector_value equals the value of selector, then the statement associated with that selector_value runs, and the CASE statement ends. Subsequent selector_values are not evaluated.

Caution:

A statement can modify the database and invoke nondeterministic functions. There is no fall-through mechanism, as there is in the C switch statement.

ELSE statement [statement ]...

The statements run if and only if no selector_value has the same value as selector.

Without the ELSE clause, if no selector_value has the same value as selector, the system raises the predefined exception CASE_NOT_FOUND.

label

A label that identifies the statement (see "statement ::=" and "label").

searched_case_statement

WHEN boolean_expression THEN statement

The boolean_expressions are evaluated sequentially. If the value of a boolean_expression is TRUE, the statement associated with that boolean_expression runs, and the CASE statement ends. Subsequent boolean_expressions are not evaluated.

Caution:

A statement can modify the database and invoke nondeterministic functions. There is no fall-through mechanism, as there is in the C switch statement.

ELSE statement [statement ]...

The statements run if and only if no boolean_expression has the value TRUE.

Without the ELSE clause, if no boolean_expression has the value TRUE, the system raises the predefined exception CASE_NOT_FOUND.

label

A label that identifies the statement (see "statement ::=" and "label").

Examples

Example 3-2, "Printing BOOLEAN Values"
Example 4-6, "Simple CASE Statement"
Example 4-7, "Searched CASE Statement"