update alarm set alarm.level=(select max(info.alarmlevel) from info,cause where alarm.cause=cause.cause and cause.id=info.probablecause) where exists (select 1 from info,cause where alarm.cause=cause.cause and cause.id=info.probablecause);这样就可以了
调试欢乐多
where alarm.cause=cause.cause
and cause.id=info.probablecause
lizhaogui() sqlserver写法
(select info.alarmlevel from info where alarm.cause=info.cause
and cause.id=info.probablecause )