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数据库-表别名帮助编译器正确解析

declare @abc table( name nvarchar(20), thedate nvarchar(20) ) insert into @abc values(a,a2) insert into @abc values(b,b2) insert into @abc values(c,c2) insert into @abc values(b,b3) select * from  (select ROW_NUMBER()over(partition by name order by thedate desc) as idd,name,thedate from @abc where thedate is not null )tt where tt.idd=1


像上面那样不会报错,可如果像下面这样就报错,可能是编译器不知道dd是哪个表的字段,无法编译所致,加了tt的话,编译器就知道idd是哪个表的字段了,可以编译。

select * from  (select ROW_NUMBER()over(partition by name order by thedate desc) as idd,name,thedate from @abc where thedate is not null ) where idd=1

 

完。

 

数据库-表别名帮助编译器正确解析