MySQL functions, IF, CASE

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IF function

syntax：

IF(expr,if_true_expr,if_false_expr)

CASE expression

syntax：

 CASE value
 WHEN compare_value_1 THEN result_1
 WHEN compare_value_2 THEN result_2
 …
 ELSE result END

second form：

 CASE
 WHEN condition_1 THEN result_1
 WHEN condition_2 THEN result_2
 …
 ELSE result END

CASE statement  (for Stored Procedure)

syntax:

 CASE  case_expression
    WHEN when_expression_1 THEN commands
    WHEN when_expression_2 THEN commands
    ...
    ELSE commands
 END CASE;