如何使用连接从两个不同的表中检索两个聚合列？

Question

我想从 ITEMS TABLE 中检索 Price Column 的总和并将其与 GOODS TABLE 相结合。问题是当我尝试连接这些表时，Goods Table 中数量列 gQnty 的总和给出 84 而不是 DISH A 的 14。任何人都可以帮助我如何完成这项任务，我可以通过相同的查询获得确切的数量 gQnty 和价格 iPrice。

TABLE 商品

gID | gName | gQnty
-------------------------
1     DISH A   10
2     DISH B   12
3     DISH A   4

TABLE 项：

iID | gID | iItem | iPrice
--------------------------
1      1    Sugar    200
2      1    Milk     300
3      1    Fruits   100

4      2    Oil      200

5      3    Sugar    100
6      3    Milk     50
7      3    Fruits   40

我的查询：

select g.gName, sum(g.gQnty)[gQnty], sum(i.iPrice)[iPrice]
from goods g join items i
on g.gID = i.gID
group by g.gName

预期结果：

gName  | gQnty | iPrice
----------------------------
DISH A |  14   |  790  
DISH B |  12   |  100

Answer 1

LEFT JOIN 是个好主意

WITH A AS (
SELECT gName, SUM(ITEMS.iPrice) AS iPrice
FROM GOODS
LEFT JOIN ITEMS
ON GOODS.gID = ITEMS.gID
GROUP BY gName 
)
SELECT gName, 
(SELECT SUM(gQnty) FROM GOODS WHERE GOODS.gName = A.gName GROUP BY gName ) AS gQnty,
iPrice
FROM A

dbfiddle

Answer 2

试试这个

select g.gName, max(g.gQnty)[gQnty], sum(i.iPrice)[iPrice]
from goods g join items i
on g.gID = i.gID
group by g.gName

甚至

select g.gName, avg(g.gQnty)[gQnty], sum(i.iPrice)[iPrice]
from goods g join items i
on g.gID = i.gID
group by g.gName

如何使用连接从两个不同的表中检索两个聚合列？

How to retrieve two aggregate columns from two different tables using joins?

sql-server

join

group-by

aggregate-functions