mysql - 多表 JOIN 问题

Question

首先，你应该知道我在 SQL 上很烂。

这是我的问题:

我有 4 个表需要连接(用于 SphinxSearch)，这是粗略的结构:

账户

Id Name Category
----------------
1  Test 1
2  Foo  2
3  Bar  1

类别

Id Name
-------
1  Restaurants
2  Store

Accounts_has_subcategory

account_id subcat_id
--------------------
1          1
1          3
2          2

子类别

Id Name
-------
1  Chinese
2  Sportswear
3  Delivery

我想要的是一个看起来像这样的结果集:

accounts.id | accounts.name | category_name | subcategories
-----------------------------------------------------------
1             Test            Restaurants     Chinese, Delivery
2             Foo             Store           Sportswear

我的查询是这样的:

SELECT a.id, a.name, c.name as category, group_concat(subcat.name) as subcategories
FROM accounts AS a
JOIN (account_has_subcategory AS ahs, subcategory AS subcat)
ON (a.id = ahs.account_id AND ahs.subcat_id = subcat.id),
accounts AS a2
JOIN category AS c
ON a2.category = c.id

如前所述，我很讨厌 SQL(只要它涉及多个连接或类似的东西，基本上...)。如果有人能给我指出正确的方向或提供解决方案(有基本的解释，这样我就可以试着把它记在脑子里 -_-)，那将是我的一天，因为我已经为这个问题奋斗了 5 个小时现在……

谢谢。

Answer 1

试试这个？

SELECT a.id, a.name, 
       c.name as category, 
       group_concat(subcat.name) as subcategories
FROM accounts AS a
INNER JOIN account_has_subcategory AS ahs ON a.id = ahs.account_id
INNER JOIN subcategory AS subcat ON subcat.id = ahs.subcat_id
INNER JOIN category AS c ON a.category = c.id
GROUP BY a.id, a.name, c.name
ORDER BY a.id;