MySQL 存储过if语句用法，MySQL IF语句允许您根据表达式的某个条件或值结果来执行一组SQL语句。

 1，if 结构

          IF expression THEN 
         statements;
    END IF;

            IF expression THEN

statements;
ELSE
else-statements;
END IF;

IF expression THEN
statements;
ELSEIF elseif-expression THEN
elseif-statements;
ELSE
else-statements;
END IF;

    2，if实例

    DELIMITER $$

CREATE PROCEDURE GetCustomerLevel(
in p_customerNumber int(11),
out p_customerLevel varchar(10))
BEGIN
DECLARE creditlim double;

SELECT creditlimit INTO creditlim
FROM customers
WHERE customerNumber = p_customerNumber;

IF creditlim > 50000 THEN

SET p_customerLevel = 'PLATINUM';
ELSEIF (creditlim <= 50000 AND creditlim >= 10000) THEN
SET p_customerLevel = 'GOLD';
ELSEIF creditlim < 10000 THEN
SET p_customerLevel = 'SILVER';
END IF;

END$$

if用在存储过程中，多多实际实践，增加动手能力
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