DECODE(x,y(i),...,z) 

DECODE(x,y(i),...,z) is a special function that decodes expressions in accordance with their values.

x	check_expression	Expression for which a comparison is to be carried out with the values in y(i)
y(i)	search_and_result_spec	<search_and_result_spec> ::= <search_expression>, <result_expression> (y(i)=u(i),v(i), i=1,...) Combination of the comparison value u(i) and the value v(i) that is to replace this comparison value
z	default_expression	Optional default value (LONG value is permissible)
u(i)	search_expression	Comparison value that is to be replaced by v(i) if it matches x
v(i)	result_expression	Value that is to replace the value u(i), if necessary (LONG value is permissible)

Examples

SQL Tutorial, Converting Values

Explanation

Both x and u(i) must have identical data types. 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.

DECODE compares the values of x with the values u(i) consecutively. If a match is found, the result of DECODE is the value v(i) in the combination y(i)=u(i),v(i).

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, DECODE supplies the result of z. If z is not specified, the NULL value is the result of DECODE.