求教sql

Question

select a.TrainNo,a.Amount,b.Carried,a.Amount-b.Carried Leave,b.Carried/a.Amount ratio
from A a,B b
where a.TrainNo=b.TrainNo

Answer 1

b.Carried必须合计（所有Type的都加在一起）

Answer 2

select a.TrainNo,a.Amount,b.Carried,a.Amount-b.Carried Leave,b.Carried/a.Amount ratio
from a,(select TrainNo,sum(Carry) Carried from b group by TrainNo) b where a.TrainNo=b.TrainNo;

Answer 3

select a.TrainNo,a.Amount,b.Carried,a.Amount-b.Carried Leave,b.Carried/a.Amount ratio
from A a,
(select TrainNo,Sum(Carry) Carried
 from B 
 group by TrainNo 
)
where a.TrainNo=b.TrainNothat's it