OQL Case Expression
1 Description
The CASE
expression is a conditional expression, similar to if/else statements in other programming languages. Each condition is an expression that returns a Boolean result. If the condition’s result is true, the value of the CASE
expression is the result that follows the condition, and the remainder of the CASE
expression is not processed. If the condition’s result is not true, any subsequent WHEN
clauses are examined in the same manner. If no WHEN
condition yields true, the value of the CASE
expression is the result of the ELSE
clause. If the ELSE
clause is omitted and no condition is true, the result is null.
2 Usage
The CASE
expression can be used in two ways – simple:
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or extended:
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3 Syntax
3.1 input_expression
input_expression
will be compared to when_expression
. If input_expression
matches when_expression
, the result of the whole CASE
expression will be result_expression
given after THEN
.
3.2 when_expression
when_expression
will be compared to input_expression
. When input_expression
matches this when_expression
, the result of the whole CASE
expression will be result_expression
given after THEN
.
3.3 boolean_expression
boolean_expression
must result in a Boolean value. When this expression returns true, the result of the whole CASE
expression will be result_expression
given after THEN
.
3.4 result_expression
result_expression
is the possible result of the whole CASE
expression.
3.5 else_result_expression
else_result_expression
is the result of the whole CASE
expression, when no result_expression
is possible.
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