mysql case when then用法

case when then 的基本用法

SELECT
	CASE
WHEN b.is_leave = 0 THEN
	'在职'
WHEN b.is_leave = 1 THEN
	'离职'
ELSE '状态为空'
END
FROM
	sys_user_front a
LEFT JOIN sys_org_emp b ON a.info_id = b.info_id
WHERE
	1 = 1
AND a.login_name = '3111111';

下面两种方法等效

SELECT
	CASE
WHEN (a.type = 1 OR a.type = 3) THEN
	'已审批'
WHEN 2 THEN
	'拒绝'
ELSE
	'审批中'
END AS tpp,
 a.*
FROM
	info a;

SELECT
	CASE a.type
WHEN 1 THEN
	'已审批'
WHEN 3 THEN
  '已审批'
WHEN 2 THEN
	'拒绝'
ELSE
	'审批中'
END AS tpp,
 a.*
FROM
	info a;