sample:
select CASE usertype WHEN 1 '管理员' WHEN 2 THEN '策划' WHEN 3 THEN '测试员' ELSE '未定义' AS usertype FROM users
二、IF( exp, value, value)
IF (1 = 1,'A','B')
select CASE usertype WHEN 1 '管理员' WHEN 2 THEN '策划' WHEN 3 THEN '测试员' ELSE '未定义' AS usertype FROM users
IF (1 = 1,'A','B')