php - MySQL编码问题

Question

当 user_id = '". $user_id . "' 时，如何使用 users_friends.user_id 加入 users

当 friend_id = '". $user_id . "' 时，将 users 加入 users_friends.friend_id

if user_id = '". $user_id . "'

INNER JOIN users ON users_friends.user_id = users.user_id

if friend_id = '". $user_id . "'

INNER JOIN users ON users_friends.friend_id = users.user_id

当前的 MySQL 代码。

SELECT COUNT(user_id) as friends
FROM users_friends
WHERE (user_id = '" . $user_id . "' 
OR friend_id = '" . $user_id . "')
AND friendship_status = '1'

Answer 1

 (SELECT * FROM users_friends JOIN users ON users.user_id = users_friends.friend_id 
    WHERE   users_friends.friend_id = '" . $user_id . "')
 UNION
 (SELECT * FROM users_friends JOIN users ON users.user_id = users_friends.user_id 
    WHERE users_friends.user_id = '" . $user_id . "')

类似这样的东西可能会起作用。

当您查看 user_friends 表时，您应该使用它来连接 users 表。