mysql - 与 MySQL 相交

Question

SELECT friend_id FROM friendships WHERE user_id = 1;

Returns:
+-----------+
| friend_id |
+-----------+
|         2 |
|         3 |
+-----------+

SELECT friend_id FROM friendships WHERE user_id = 2;

Returns:
+-----------+
| friend_id |
+-----------+
|         1 |
|         3 |
|         6 |
+-----------+

我正在尝试为 MySQL 寻找 INTERSECT 的替代方案。我需要获取这两个查询之间的公共(public)行。

Answer 1

您可以使用联接来替换INTERSECT

SELECT DISTINCT f1.friend_id 
FROM friendships f1
JOIN friendships f2 ON f1.friend_id = f2.friend_id
WHERE f1.user_id = 1 and f2.user_id = 2;