MySQL使用IF语句及用case语句对条件并结果进行判断 

CREATE TABLE `t1` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
`jgid` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;

INSERT INTO `avlicy`.`t1`(`id`, `name`, `jgid`) VALUES (1, ‘二二’, 2);
INSERT INTO `avlicy`.`t1`(`id`, `name`, `jgid`) VALUES (2, ‘李四’, 2);
INSERT INTO `avlicy`.`t1`(`id`, `name`, `jgid`) VALUES (4, ‘七七’, 3);
INSERT INTO `avlicy`.`t1`(`id`, `name`, `jgid`) VALUES (5, ‘小猕猴’, 1);
INSERT INTO `avlicy`.`t1`(`id`, `name`, `jgid`) VALUES (6, ‘小米粥’, 1);
INSERT INTO `avlicy`.`t1`(`id`, `name`, `jgid`) VALUES (7, ‘小哈吧’, 1);

SELECT
t1.*,
IF(MOD(t1.id,2)=0 ,’是’,’否’) AS 是否被二整除
FROM
t1

SELECT
t1.*
FROM
t1
WHERE
IF( MOD ( t1.id, 2 )= 0, id = jgid, id <> jgid )

SELECT
*,
CASE
WHEN jgid = 1 THEN
‘学生’
WHEN jgid = 2 THEN
‘教师’
WHEN jgid = 3 THEN
‘家长’ ELSE ”
END AS ‘角色’
FROM
t1