Update @A set Column1 = minC
from (select Ab.Column2, min(C.Column1) as minC
from @A Ab
inner join B on Ab.Column2 = B.Column2
inner join C on C.column2 = B.Column2 --No need to add again the A.col2 = B.col2
inner join D on D.column1 = B.column2
group by Ab.Column2) Grouped where Column2 = Grouped.Column2
和
Update @A set Column1 = minC
from (select Ab.Column2, min(C.Column1) as minC, B.column2 as tempcolumn
from @A Ab
inner join B on Ab.Column2 = B.Column2
inner join C on C.column2 = B.Column2 --No need to add again the A.col2=B.col2
group by Ab.Column2) Grouped
inner join D on D.column1 = Grouped.tempcolumn
where Column2 = Grouped.Column2
2个查询的结果有什么区别吗?