Question

我有以下表格，需要进行查询

Clubs( club_id, name )
Facilities ( id, club_id, name )

逻辑是俱乐部可以拥有一个或多个设施，我需要一个简单的查询来基本搜索所有拥有某些设施的俱乐部

例如。所有俱乐部都有足球和网球场设施

SELECT *
FROM (`clubs`)
JOIN `club_facilities` ON `club_facilities`.`club_id` = `clubs`.`id`
WHERE `facility_id` = 1
AND `facility_id` = 3

这会返回0结果 - 但是如果将其更改为以下

SELECT *
FROM (`clubs`)
JOIN `club_facilities` ON `club_facilities`.`club_id` = `clubs`.`id`
WHERE `facility_id` = 1
OR `facility_id` = 3

我从数据库中得到两个结果（行） - 我认为我需要做一些额外的自我加入，但不完全确定如何做到这一点。任何人都可以提出一些建议。

由于

Answer 1

两次加入设施表。

SELECT * FROM clubs 
JOIN club_facilities f1 ON club_id = clubs.id
JOIN club_facilities f2 ON club_id = clubs.id
WHERE f1.facility_id = 1
    AND f2.facility_id = 3

或使用子选择：

SELECT * FROM clubs 
WHERE EXISTS(SELECT * FROM club_facilities WHERE club_id = clubs.id AND facility_id = 1)
  AND EXISTS(SELECT * FROM club_facilities WHERE club_id = clubs.id AND facility_id = 3)

Answer 2

SELECT clubs.id FROM clubs JOIN club_facilities ON (club_id=clubs.id)
WHERE facility_id IN (1,3)
GROUP BY clubs.id
HAVING count(DISTINCT facility_id)=2;

将为您提供符合IN (1,3)条件的设施数量为2（即两者）的俱乐部。

MySQL Query建议＆amp;加入

2 个答案: