Question

我有3个相互关联的表，我正在尝试正确查询数据，以便获得我需要的所有内容。

以下是我拥有的3个表格：

ORDER_ITEMS

+------------+--------------+------+-----+
| order_id   | product_id   |count | max |
+------------+--------------+------+-----+
| 1AB45      | 3214         | 1    | 20  |
| YE72H      | 314          | 2    | 20  |
| HWYE1      | 5311         | 3    | 10  |
| HWYE1      | 314          | 1    | 20  | 
+------------+--------------+------+-----+

订单

+-----------+-------------+---------+-----+
| order_id  | buyer_email | user_id | ... |
+-----------+-------------+---------+-----+
|  1AB45    | user1@gmail | 123     |     |
|  YE72H    | user2@al.uk | 124     |     |
|  HWYE1    | me@mail.com | 125     |     |
+-----------+-------------+---------+-----+

reg_keys

+-----------+-------------+---------+------------+
| reg_key   | time_redeem | user_id | product_id |
+-----------+-------------+---------+------------+
|  UN-12XZ  | 2015-11-12  | 123     |    3214    |
|  UN-34AB  | 2015-10-12  | 125     |    5311    |
|  UN-67UY  | 2015-09-12  | 125     |    314     |
+-----------+-------------+---------+------------+

我希望得到所有注册码，其中count / quanity等于1且time_redeemed不为NULL。这是我的查询获得结果，但使用相同的电子邮件/ order_id覆盖所有其他订单信息：

SELECT * FROM order_items
JOIN orders ON orders.order_id = order_items.order_id
JOIN reg_keys ON reg_keys.user_id=orders.user_id and reg_keys.product_id=order_items.product_id
WHERE count=1 and reg_keys.redeemed_by is not null
GROUP BY reg_key ORDER BY time_redeem DESC

这让我没有结果。我搞砸了什么？

Answer 1

请勿使用group by并选择键列

SELECT 
    reg_keys.reg_key * 
FROM 
    order_items
JOIN 
    orders ON orders.order_id = order_items.order_id
JOIN 
    reg_keys ON reg_keys.user_id = orders.user_id 
             AND reg_keys.product_id = order_items.product_id
WHERE 
    count = 1 
    AND reg_keys.redeemed_by IS NOT NULL
ORDER BY time_redeem DESC;

复杂的MySQL查询正确连接表

1 个答案: