因为user为系统保留,所以如果你的用户表名确实为user的话,上面的写法会出错.做如下修改: select a.*,case when b.userid is null then '不在线' else '在线' end as 是否在线 from [user] a left join onlineuser b on a.userid=b.userid
select a.*,case when b.userid is null then '不在线' else '在线' end [是否在线] from [user] a left join onlineuser b on a.userid=b.userid或:select *,case when userid in (select userid from onlineuser) then '在线' else '不在线' end [是否在线] from [user]
SP_MONITOR --显示当前的SESSION的状态。
SP_WHO2 --显示当前SQL SERVER和client的连接状态和CPU,I/O的状态。
select a.*,case when b.userid is null then '不在线' else '在线' end as 是否在线
from [user] a left join onlineuser b on a.userid=b.userid