使用 Count 时选择上的 MYSQL 列别名不起作用

Question

我必须在两个名为“plays”的连接表上使用相似的列，我想区分它们，但我得到“'field list' 中的未知列 'p.plays'”。我做错了什么？

SELECT *,  
            p.plays AS pl, 
            m.plays AS mp,
            COUNT(p.sid) frequency,    
FROM        music m
            JOIN plays p
            ON p.sid = m.sid
            INNER JOIN users u
            ON u.uid = m.uid
            INNER JOIN downloads d
            ON d.sid = m.sid        
WHERE       p.time > NOW() - INTERVAL 3 DAY 
            AND p.sid != '' 
            AND m.perms != 'c' 
GROUP       BY m.sid
ORDER       BY frequency DESC
            LIMIT 50

图像。

表格：音乐

表格：播放

谢谢。

Answer 1

根据您在编辑中提供的表格架构。您在 plays 表中没有 Plays 列，这就是您收到此错误的原因尝试删除此 p.Plays

SELECT *,  

            m.plays AS mp,
            COUNT(p.sid) frequency,    
FROM        music m
            JOIN plays p
            ON p.sid = m.sid
            INNER JOIN users u
            ON u.uid = m.uid
            INNER JOIN downloads d
            ON d.sid = m.sid        
WHERE       p.time > NOW() - INTERVAL 3 DAY 
            AND p.sid != '' 
            AND m.perms != 'c' 
GROUP       BY m.sid
ORDER       BY frequency DESC
            LIMIT 50