如何从多个表中总价？

Question

我需要从多个表格中获得总价格。

这是SQL SERVER查询

Select 
sum(Tbl_StartupBanner.Price + Tbl_SignInBanner.Price + Tbl_SignOutBanner.Price) as Total
from Tbl_StartupBanner,Tbl_SignInBanner,Tbl_SignOutBanner

Tbl_StartupBanner - Price Value - 1 
Tbl_SignInBanner   - Price Value - 1
Tbl_SignOutBanner - Price Value is None .. There is No record in This table  ... 

但我需要的总数是：2

Answer 1

试试这个

SELECT TableA.Column1 + TableB.Column2 FROM TableA 
LEFT JOIN TableB ON TableA.MatchingColumn = TableB.MatchingColumn

Answer 2

Select 
ISNULL(t1.Price, 0) + ISNULL(t2.Price, 0) + ISNULL(t3.Price, 0) as Total
from Tbl_StartupBanner t1
LEFT JOIN Tbl_SignInBanner t2 ON t1.MatchCol = t2.MatchCol
LEFT JOIN Tbl_SignOutBanner t3 ON t1.MatchCol = t2.MatchCol