舉個例子：

測試數據：

????usernam? age

1?? lili????????????19

2? toto????????? 17

select username,(case age?

????????????????????????????when 19 then '成年人'?

????????????????????????????when 17 then '未成年人'

????????????????????????????else 'xx') as age_str

from users;

查詢結果：

??? username?? age_str

1???? lili??? ????????????成年人

2???? toto??????????? 未成年人