ORDER BY column FROM another table

Question

我想通过 last_act 和他们一起订购用户的朋友。但是有关用户的信息在 table users 和 last_act 中 table 朋友.

我试过了，但没用：

SELECT m.* 
FROM users AS m 
WHERE m.username = '$username' 
JOIN friends AS p 
ORDER BY p.last_act DESC

Answer 1

您应该有一个用户朋友 table 的外键。例如，说它是 userid。那么上面的查询将是：

SELECT m.* 
FROM users AS m 
    JOIN friends AS p ON p.userid = m.id  
WHERE m.username = '$username' 
ORDER BY p.last_act DESC

Answer 2

SELECT m.*, f.* 
FROM users AS m  
JOIN friends AS p 
ON m.id = p.user_id
LEFT JOIN users AS f 
ON p.friend_id = f.id
WHERE m.username = '$username' 
ORDER BY p.last_act DESC

Answer 3

你的问题太笼统了，我们不知道表的结构，也没看到报错信息...

但是发现有顺序问题，它必须按 SELECT、FROM、JOIN、WHERE 进行。并且您需要使用 ON 来映射 JOIN 中的关系。

示例

SELECT * FROM table1 JOIN table2 ON table1.id = table2.foreign_id

ORDER BY column FROM another table

ORDER BY column FROM another table

mysql

sql-order-by

multiple-columns