将结果结合在两个表中

Question

有two tables (Table1 and Table2)具有相同的列。

Customerno, amount 

还有第三个表Customers与列：

Customerno, customername 

目前，以下两个查询运行，并使用Excel来源的组合的结果（VLOOKUP等）

Select a.customerno, b.customername, sum(a.amount) 
FROM Table1 a join customers b on a.Customerno = b.Customerno 
group by a.customerno, b.customername 


Select a.customerno, b.customername, sum(a.amount) 
FROM Table2 a join customers b on a.Customerno = b.Customerno 
group by a.customerno, b.customername 

将这两个查询合并为一个以获得所需结果的正确方法是？

Answer 1

Select a.customerno, b.customername, sum(a.amount) 
FROM 
( 
    SELECT Customerno, amount FROM Table1 
    UNION ALL -- use this keep duplicates ie amounts from both tables 
    -- UNION -- will discard duplicates 
    SELECT Customerno, amount FROM Table2 
) a 
join customers b on a.Customerno = b.Customerno 
group by a.customerno, b.customername 

Answer 2

您需要为此使用UNION声明。这是联合这两者的最简单方法，你可以从这里开始工作。

select * 
from 
(

Select a.customerno, b.customername, sum(a.amount) 
FROM Table1 a join customers b on a.Customerno = b.Customerno 
group by a.customerno, b.customername 

union -- or union all if you want to keep the duplicates 

Select a.customerno, b.customername, sum(a.amount) 
FROM Table2 a join customers b on a.Customerno = b.Customerno 
group by a.customerno, b.customername 
) P