mysql数据库字段判断语句
一、CASE field WHEN value THEN value WHEN ... THEN ... ELSE ...

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')