定义

IF-THEN-ELSE语句通常用在根据不同条件执行不同SQL的场景。

语法

IF condition1 THEN
   {...statements to execute when condition1 is TRUE...}

[ ELSEIF condition2 THEN
   {...statements to execute when condition2 is TRUE...} ]

[ ELSE
   {...statements to execute when both condition1 and condition2 are FALSE...} ]

END IF;

参数

例子

DELIMITER //

CREATE FUNCTION IncomeLevel ( monthly_value INT )
RETURNS varchar(20)

BEGIN

   DECLARE income_level varchar(20);

   IF monthly_value <= 4000 THEN
      SET income_level = 'Low Income';

   ELSEIF monthly_value > 4000 AND monthly_value <= 7000 THEN
      SET income_level = 'Avg Income';

   ELSE
      SET income_level = 'High Income';

   END IF;

   RETURN income_level;

END; //

DELIMITER ;