你是用left join 还是inner join?
试试这个:
select A.Weight,A.ProductDesc,A.Direction,B.TotalWeight
from A inner join B on A.ProductDesc=B.ProductDesc
and A.Direction=B.Direction
select aa..Weight,aa..ProductDesc,aa.Direction,bb..TotalWeight
from A aa,B bb
where aa.ProductDesc=bb.ProductDesc and aa.Direction=bb.Direction;