为什么这个删除重复记录的语句不能执行，不能使用另名吗？
delete from
from osrd a
where a.myid !=
(select max(myid) from osrd b where b.ItemCode=a.ItemCode and b.DocType=a.DocType and b.DocEntry=a.DocEntry and b.DocLineNum=a.DocLineNum)

错误信息：
服务器: 消息 156，级别 15，状态 1，行 2
在关键字 'from ' 附近有语法错误。


[解决办法]
delete from osrd a
where a.myid !=
(select max(myid) from osrd b where b.ItemCode=a.ItemCode and b.DocType=a.DocType and b.DocEntry=a.DocEntry and b.DocLineNum=a.DocLineNum)
[解决办法]
delete from
from osrd a

两个from ,笔误？
[解决办法]
多了from ，前面的那from改a

[解决办法]
用exists应该效率会好一点:
delete a from
from osrd a
where exists
(select max(myid) from osrd b where b.ItemCode=a.ItemCode and b.DocType=a.DocType and b.DocEntry=a.DocEntry and b.DocLineNum=a.DocLineNum and myid> a.myid)