左加入一些数据

Question

我有两个 mySQL 表（订单和详细信息），我想获取 type = sale 和 [=15] 的所有订单（包括 date 和 amount） =] 对于特定的 affiliate.

到目前为止，我可以 post 尝试 20 种不同的方法，但其中 none 有效，这将是对 space 的浪费。我对此很着急，但查看其他 Whosebug 问题并没有帮助。

+--------------------------------------------+
|                    orders                  |
+---------+----------+------------+----------+
| orderID | type     |    date    |  status  |
+---------+----------+------------+----------+
|    1    | sale     | 11/01/2020 | complete |
|    2    | sale     | 12/01/2020 | pending  |
|    3    | sale     | 13/01/2020 | complete |
|    4    | sale     | 14/01/2020 | complete |
|    5    | giveaway | 15/01/2020 | complete |
+---------+----------+------------+----------+

+-----------------------------+
|           details           |
+---------+-----------+-------+
| orderID |    key    | value |
+---------+-----------+-------+
|    1    | amount    |  30   |
|    1    | affiliate |  999  |
|    2    | amount    |  40   |
|    2    | affiliate |  999  |
|    3    | amount    |  60   |
|    3    | affiliate |  333  |
|    4    | amount    |  70   |
|    5    | amount    |  80   |
+---------+-----------+-------+

affiliate = 999

的预期输出

+---------+-------------+--------+
| orderID |    date     | amount |
+---------+-------------+--------+
|    1    | 11/01/2020  |     30 |
+---------+-------------+--------+

Answer 1

您必须加入 orders 到 details 的 2 个副本：

select o.orderID, o.date, d2.value amount
from orders o
inner join details d1 on d1.orderID = o.orderID and d1.key = 'affiliate' and d1.value = 999
inner join details d2 on d2.orderID = o.orderID and d2.key = 'amount'
where o.status = 'complete'

参见demo。
结果：

> orderID | date       | amount
> ------: | :--------- | -----:
>       1 | 11/01/2020 |     30

Answer 2

一个选项使用两个连接：

select o.orderid, o.date, sum(dam.value) amount
from orders o
inner join details daf on daf.orderid = o.orderid 
inner join details dam on dam.orderid = o.orderid
where 
    and o.status = 'complete'
    and daf.key = 'affiliate' and daf.value = 999
    and dam.key = 'amount'

您还可以使用单连接和条件聚合：

select o.orderid, o.date, 
    sum(case when d.key = 'amount' then d.value else 0 end) amount
from orders o
inner join details d on d.orderid = o.orderid 
where o.status = 'complete'
group by o.orderid
having max(d.key = 'affiliate' and d.value = 999) = 1

左加入一些数据

LEFT JOIN some data WHERE

mysql

sql

inner-join