具有计数的非聚合列答案

【问题标题】：Non aggregated Column with Count具有计数的非聚合列
【发布时间】：2021-04-04 02:02:38
【问题描述】：

我对 MySQL 很陌生，我正在尝试制作一个计数和显示喜欢的事件页面。我得到错误：

Error details: SQLSTATE[42000]: Syntax error or access violation: 1055 Expression #10 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'db.events_likes.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

我无法更改 SQL 模式，所以我想知道是否有办法聚合列？

代码：

SELECT  *, eventid, COUNT(events_likes.id) AS likes, GROUP_CONCAT(users.fname SEPARATOR '|') AS liked_by FROM  events
     LEFT JOIN events_likes 
     ON events.eventid = events_likes.event

     LEFT JOIN users
     ON events_likes.user = users.id
     GROUP BY events.eventid

【问题讨论】：

标签： php mysql phpmyadmin

【解决方案1】：

问题在于SELECT * 中的*

您要求 MySQL 返回目标表中的每一列，但其中一些未聚合 (event_likes.id)。

仅列出您需要的列。

SELECT  eventid, COUNT(events_likes.id) AS likes, GROUP_CONCAT(users.fname SEPARATOR '|') AS liked_by FROM  events
 LEFT JOIN events_likes 
 ON events.eventid = events_likes.event

 LEFT JOIN users
 ON events_likes.user = users.id
 GROUP BY events.eventid

【讨论】：