mysql：请求的分组结果

我的sql请求为我提供：

        SELECT 
        sf_guard_user.id, sf_guard_user.username, sf_guard_user.avatar_time, fromid, toid,sum(chatMessage.fromidlu) - sum(chatMessage.toidlu) as nonlus
        FROM chatMessage, sf_guard_user
        WHERE (chatMessage.fromid = sf_guard_user.id AND toid=16595 AND toidhidden=0) OR (chatMessage.toid = sf_guard_user.id AND fromid=16595 AND fromidhidden=0)
        GROUP by fromid

我想对这个结果应用另一个SQL，所以最终结果是在“nonlus”上求和

SELECT id, username, avatar_time, fromid, toid, sum(nonlus) FROM 
**this request**
order by id

我试过了

SELECT id, username, avatar_time, fromid, toid, sum(nonlus) FROM (
          SELECT 
            sf_guard_user.id, sf_guard_user.username, sf_guard_user.avatar_time, fromid, toid,sum(chatMessage.fromidlu) - sum(chatMessage.toidlu) as nonlus
            FROM chatMessage, sf_guard_user
            WHERE (chatMessage.fromid = sf_guard_user.id AND toid=16595 AND toidhidden=0) OR (chatMessage.toid = sf_guard_user.id AND fromid=16595 AND fromidhidden=0)
            GROUP by fromid)
Group by id

但是得到错误

每个派生表都必须有自己的别名

---

您只需将别名分配给内部

选择
，请尝试以下操作：

SELECT id, username, avatar_time, fromid, toid, sum(nonlus) FROM (
          SELECT 
            sf_guard_user.id as id, sf_guard_user.username as username, sf_guard_user.avatar_time as avatar_time, fromid, toid, sum(chatMessage.fromidlu) - sum(chatMessage.toidlu) as nonlus
            FROM chatMessage, sf_guard_user
            WHERE (chatMessage.fromid = sf_guard_user.id AND toid=16595 AND toidhidden=0) OR (chatMessage.toid = sf_guard_user.id AND fromid=16595 AND fromidhidden=0)
            GROUP by fromid) a
Group by a.id

按照字面意思，只需在你的
后面键入字母
a
）
在你的第一个
分组人之后。关于这一点，有数百个问题。您是否尝试简单地将错误消息放入SO的搜索框中？您应该学会使用显式的
JOIN
而不是交叉乘积。当您按id分组时，select中的任何列（如果不是按列分组）都需要进行聚合。@PeterHe MySQL允许这样做。对于由分组列唯一定义的列，它不是必需的。它取决于sql_模式，并且可能会得到意外的结果。标准sql不允许这样做。