sql 中为数据库中没有的字段根据 某字段赋值

SELECT CASE WHEN(memberAge<18) THEN '少年' WHEN(memberAge>=18 and memberAge <30) THEN '青年' WHEN(memberAge>=30 and memberAge<50) THEN '中年' ELSE '老年' END AS ageMeno,sk.*  FROM `sk_member` sk;