從SQL Server中的表中選擇加入和總和

Question

Id  Item 
-------------- 
1  ItemA 
2  ItemB 
3  ItemC 

itemid  Price 
---------------- 
1   4 
1   3 
1   9 
2   2 
2   4 
2   3 

如何從2個表中選擇總和？就像爲：

ItemA 16 
ItemB 9 
ItemC 0 

Answer 1

您可以使用LEFT JOINJOIN表和應用聚合函數SUM()到price領域：

select t1.item, IsNull(sum(t2.price), 0) total 
from table1 t1 
left join table2 t2 
    on t1.id = t2.itemid 
group by t1.item 

見SQL Fiddle with Demo

的LEFT JOIN將允許記錄不在第二個表中包含在最終結果中。我將IsNull()添加到sum()以將任何null值替換爲零。

結果：

| ITEM | TOTAL | 
----------------- 
| ItemA | 16 | 
| ItemB |  9 | 
| ItemC |  0 | 

Answer 2

請嘗試：

select a.Item, ISNULL(SUM(b.Price), 0) AS TOTALSum 
from Table1 a LEFT JOIN Table2 b on a.Id=b.ItemId 
Group by a.Item 

Answer 3

試試這個

select item,sum(price) from table1 left outer join table2 
on table1.id=table2.itemid 
group by item