Question

我有两个不同的表

bills
billId | bar     | drinker  | date     | time
0001   | SomeBar |  Jon Doe | 11-13-18 | 08:10
0002   | SomeBar |  Jane Doe| 11-10-18 | 10:10
0003   | twoBar  |  Mike Doe| 11-11-18 | 12:12

transactions
billID | item | quantity
0001   | bud  | 3
0002   | bud  | 3
0003   | coors| 1

一个酒吧出售的啤酒总数如何相加？我知道我可以使用内部联接，因为它们都共享一个billId，并且我理解此查询来计算单个表的总数将是这样的。

SELECT item, SUM(quantity) AS TotalQuantity
FROM transactions
GROUP BY item
ORDER BY SUM(quantity) DESC; 

Select * FROM bills inner JOIN transactions ON bills.billId = transactions.billID AND bar = SOMEBAR;

Answer 1

您已经接近了，但是您应该使用GROUP BY语句对要分组的变量进行分组：

SELECT b.bar, sum(t.quantity) as total
FROM bills b INNER JOIN transactions t ON b.billId = t.billId
GROUP BY b.bar;

Answer 2

您可以像这样加入bills表并按bar分组：

SELECT bar, SUM(quantity)
FROM transactions t
    JOIN bills b USING (billID)
GROUP BY b.bar;

从两个表中获取总销售数据

2 个答案: