mysql case when then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';

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;