oracle 使用left join
select plate.plateID,PlateName,PlateState,PlateRemarks,Topic.TopicTitle,AnswerCountA,userInfo.username
from plate
left join Topic
on Topic.plateID=plate.plateID and TopicTope='置顶帖'
left join userInfo
on Topic.userID=userInfo.userID
left join (select TopicID,count(*) as AnswerCountA
from Answer group by TopicID) as userTopic
on Topic.TopicID = userTopic.TopicID
where ParentID=:ParentID
这个语句在as那里报错,显示缺少关键字,这是什么错?我之前在SQL 2008里运行过是正确的,但是在ORACLE里面就有问题。。有没有大神可以解释下??