Simple CASE Function (simple_case_function) 

The simple CASE function (simple_case_function) is a special function that analyzes a quantity of simple expressions to determine a (result_expression).

Syntax

<simple_case_function> ::=
CASE <check_expression>,
        WHEN <search_expression> THEN <result_expression>
            [...]
        [ELSE <default_expression>])
END

<check_expression> | <search_expression> | <result_expression> | <default_expression> ::= <expression>

expression

Explanation

x	check_expression	Expression x for which a comparison is to be carried out with the comparison values u(i)
u(i)	search_expression	Comparison value u(i). The function delivers v(i) as the result at the first match of u(i) with x.
v(i)	result_expression	Value v(i) that is to be accepted, if u(i) matches x
z	default_expression	Value z, optional default value

CASE compares the values of x with the values u(i) consecutively. If a match is determined, the result of the simple CASE function is the value v(i) associated with u(i).

The data types of x and u(i) must be comparable. The data types of v(i) and z must be comparable. The data types of u(i) and v(i) do not have to be comparable.

A match is present if x and u(i) are NULL values. The comparison of the special NULL value with any other value never results in a match.

If a match is not found, CASE supplies the result of z. If z is not specified, the NULL value is the result of CASE.

See also:

General CASE Function (searched_case_function)