在多个列和条件上左连接

k2fxgqgv 于 2021-07-29 发布在 Java

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我有两张table，一张是订单，一张是产品

ORDERS TABLE 

+----------+-----------+--------+---------------------+----------+----------+---------------------+--------+
| order_id | order_by  | status | created_at          | product1 | product2 | delivery_date       | pickup |
+----------+-----------+--------+---------------------+----------+----------+---------------------+--------+
|        1 | Maria     |      0 | 2020-07-19 00:00:00 |        1 |        3 | 2020-07-17 00:00:00 |      0 |
|        2 | Joao      |      0 | 2020-07-20 00:00:00 |        2 |        0 | 2020-07-20 00:00:00 |      0 |
|        3 | Jose      |      1 | 2020-07-20 00:00:00 |        3 |        0 | 2020-07-20 00:00:00 |      0 |
|        4 | Matias    |      0 | 2020-07-19 23:50:40 |        1 |        3 | 2020-07-19 00:00:00 |      0 |
|        5 | Matias    |      0 | 2020-07-19 23:50:40 |        1 |        3 | 2020-07-19 00:00:00 |      0 |
|        6 | Joaozinho |      0 | 2020-07-19 00:00:00 |        1 |        3 | 2020-07-22 00:00:00 |      0 |
+----------+-----------+--------+---------------------+----------+----------+---------------------+--------+

PRODUCTS TABLE

+----+-----------+-------+
| id | name      | price |
+----+-----------+-------+
|  1 | Produto 1 |    11 |
|  2 | Produto 2 |    22 |
|  3 | Produto 3 |    33 |
|  4 | Produto 4 |    44 |
|  5 | Produto 5 |    55 |
+----+-----------+-------+

EXPECTED OUTPUT

+----------+-----------+--------+---------------------+----------+----------+---------------------+--------+-----------+----------+-----------+----------+
| order_id | order_by  | status | created_at          | product1 | product2 | delivery_date       | pickup | p1_name   | p1_price | p2_name   | p2_price |
+----------+-----------+--------+---------------------+----------+----------+---------------------+--------+-----------+----------+-----------+----------+
|        1 | Maria     |      0 | 2020-07-19 00:00:00 |        1 |        3 | 2020-07-17 00:00:00 |      0 | Produto 1 |       11 | Produto 3 |      33  |
|        2 | Joao      |      0 | 2020-07-20 00:00:00 |        2 |        0 | 2020-07-20 00:00:00 |      0 | Produto 2 |       22 |   null    |     null |
|        3 | Jose      |      1 | 2020-07-20 00:00:00 |        3 |        0 | 2020-07-20 00:00:00 |      0 | Produto 3 |       33 |   null    |     null |
|        4 | Matias    |      0 | 2020-07-19 23:50:40 |        1 |        3 | 2020-07-19 00:00:00 |      0 | Produto 1 |       11 | Produto 3 |       33 |
|        5 | Matias    |      0 | 2020-07-19 23:50:40 |        1 |        3 | 2020-07-19 00:00:00 |      0 | Produto 1 |       11 | Produto 3 |       33 |
|        6 | Joaozinho |      0 | 2020-07-19 00:00:00 |        1 |        3 | 2020-07-22 00:00:00 |      0 | Produto 1 |       11 | Produto 3 |       22 |
+----------+-----------+--------+---------------------+----------+----------+---------------------+--------+------+-----------+-------+------------------+

我需要在orders表和price列的每个产品（product1，product2..）上使用不同的名称（product1\u name，product2\u name..）留下连接

sql mysql Join Database mysql-workbench

来源：https://stackoverflow.com/questions/62961511/left-join-on-multiple-columns-and-conditions

2条答案

按热度按时间

woobm2wo1#

select o.*, p1.name, p1.price
from orders o
inner join products p1 on p1.id=o.product1

添加product2应该没那么难，只是作为一种练习。。。

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wxclj1h52#

你需要两个 join 不是吗 products 表格：

select
    o.*,
    p1.name  p1_name,
    p1.price p1_price,
    p2.name  p2_name,
    p2.price p2_price
from orders o
left join products p1 on p1.id = o.product1
left join products p2 on p2.id = o.product2

如果 product1 始终可用，您可以先打开 left join 到一个 inner join ，这使得查询的效率略高。

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在多个列和条件上左连接

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