CASE
Evaluates a set of Boolean expressions to determine the result.
CASE
WHEN Boolean_expression THEN result_expression
[ ...n ]
[
ELSE else_result_expression
]
END
Arguments
- n
Is a placeholder that indicates that multiple WHEN when_expression THEN result_expression clauses, or multiple WHEN Boolean_expression THEN result_expression clauses can be used.
- THEN result_expression
Is the expression returned when Boolean_expression evaluates to true. result expression is any valid expression.
- ELSE else_result_expression
Is the expression returned if no comparison operation evaluates to true. If this argument is omitted and no comparison operation evaluates to true, CASE returns null. else_result_expression is any valid expression. The data types of else_result_expression and any result_expression must be the same or must be an implicit conversion.
- WHEN Boolean_expression
Is the Boolean expression evaluated when the searched CASE format is used. Boolean_expression is any valid Boolean expression.
Return Value
Returns the highest precedence type from the set of types in the result_expression and the optional else_result_expression.
Remarks
The Entity SQL case expression resembles the Transact-SQL case expression. You use the case expression to make a series of conditional tests to determine which expression will yield the appropriate result. This form of the case expression applies to a series of one or more Boolean expressions to determine the correct resulting expression.
The CASE function evaluates Boolean_expression for each WHEN clause in the order specified, and returns result_expression of the first Boolean_expression that evaluates to true. If no Boolean_expression evaluates to true, the Database Engine returns the else_result_expression if an ELSE clause is specified, or a null value if no ELSE clause is specified.
A CASE statement cannot return a multiset.
Example
The following Entity SQL query uses the CASE expression to evaluate a set of Boolean expressions in order to determine the result. The query is based on the AdventureWorks Sales Model. To compile and run this query, follow these steps:
Follow the procedure in How to: Execute a Query that Returns PrimitiveType Results.
Pass the following query as an argument to the
ExecutePrimitiveTypeQuerymethod:
CASE WHEN AVG({@score1,@score2,@score3}) < @total THEN TRUE ELSE FALSE END