Sqlserver case when 用法

题记：哈哈哈,今天写着写着竟然忘记了case when的用法，仅此来记录加深印象

   select case when  a.status=1 then '处理完成'
   when a.STATUS=99 then '已终止流程'
   else '处理中' end as status
   ,* from  FLOW_EQUITYBILL a  

 我们类比一下更容易理解  

case when   约等于 If     

when  约等于 满足条件执行的代码

then 后面的when  相当于 else if

end 相当于 反括号)

当然 case when 也支持多条件 and 或者or

select top 100 State, JoinState, 
(
    case 
        when State = 1 and Joinstate = 0 
        then 2 
        when State = 1 and JoinState = 1 
        then 1 
        else 0 
    end
)   as usestate 
from UserInfo