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mysql - MySql 用列名连接两个表

问题描述

我的 MySQL 数据库中有这些表：

汽车表： 

+----Cars   Table-----+
+---------------------+
| id | BMW   | KIA    |-and another cars
+----+----------+-----+
| 1  | M5    | Rio    |
| 2  | Z1    | Serato |
| 3  | X5    | Sorento|

像表：

+----------------------+-----+
| id | Cars_id| Cars   |ip   |
+----+----------+------+-----+
| 1  |   1    | KIA    |1.0.1|
| 2  |   1    | BMW    |1.0.1|

基本上，Cars 表有更多的汽车 Mark 及其型号。

我的问题是，如何加入这些表 - Like.Cars_id=Cars.id 和 Like.Cars=Cars.Column 名称？

所以，我想要这样的查询：

SELECT Cars.BMW, Cars.KIA,  COUNT(Like.ip) AS likes
FROM CARS_Table
    LEFT JOIN Like_table
        ON Cars.id = Like.Cars_id AND what?

标签： mysqlsql

解决方案

你应该这样规范化表格

Brand 
id, name  
1, BMW 
2, KIA 
3, ...

cars 
id, id_brand, car_name 
1, 1, M5 
2, 1, Z1 
3, 1, X5 
4, 2, Rio 
5, 2, Serato 
6, 2, Sorento 

like_table  

id, cars_id, ip 
1, 1, 1.0.1 
2, 1, 1.0.1 


select b.name, c.name, count(ip)
from  like_table l 
inner join  cars c on l.cars_id = c.id 
inner join  Brand b on b.id = c.id_brand
group by b.name, c.name

这样既容易获得汽车的喜欢，也容易获得品牌和其他人的喜欢

select b.name count(ip)
from  like_table l 
inner join  cars c on l.cars_id = c.id 
inner join  Brand b on b.id = c.id_brand
group by b.name

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