Conditional Operators
- reference
Case expressions evaluate conditional logic in an expression.
case-expr:
simple-case-expression | searched-case-expression
Simple Case Expressions
simple-case-expr:
CASE expression ( WHEN expression THEN expression)
[ ( WHEN expression THEN expression) ]*
[ ELSE expression ] END
Simple case expressions allow for conditional matching within an expression. The evaluation process is as follows:
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The first WHEN expression is evaluated. If it is equal to the search expression, the result of this expression is the THEN expression.
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If it is not equal, subsequent WHEN clauses are evaluated in the same manner.
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If none of the WHEN expressions are equal to the search expression, then the result of the CASE expression is the ELSE expression.
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If no ELSE expression was provided, the result is NULL.
Searched Case Expressions
searched-case-expression:
CASE ( WHEN condition THEN expression)
[( WHEN condition THEN expression ) ]*
[ ELSE expression ] END
Searched case expressions allow for conditional logic within an expression. The evaluation process is as follows:
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The first WHEN expression is evaluated.
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If TRUE, the result of this expression is the THEN expression.
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If not TRUE, subsequent WHEN clauses are evaluated in the same manner.
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If none of the WHEN clauses evaluate to TRUE, then the result of the expression is the ELSE expression.
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If no ELSE expression was provided, the result is NULL.