环境
mysql> select version(); +-----------+ | version() | +-----------+ | 8.0.16 | +-----------+
执行查询语句
mysql> select * from my_student; +----+--------+----------+------+--------+ | id | name | class_id | age | gender | +----+--------+----------+------+--------+ | 1 | 刘备 | 1 | 18 | 2 | | 2 | 李四 | 1 | 19 | 1 | | 3 | 王五 | 2 | 20 | 2 | | 4 | 张飞 | 2 | 21 | 1 | | 5 | 关羽 | 1 | 22 | 2 | | 6 | 曹操 | 1 | 20 | NULL | +----+--------+----------+------+--------+ 6 rows in set (0.00 sec) -- 需求：按照年龄排序后，取出每个班级年龄最大的学生 select * from ( select * from my_student order by age desc ) as t group by t.class_id;
报错
ERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 't.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
原因：
MySQL 5.7.5及以上功能依赖检测功能
解决办法
-- 查看当前配置项 select @@global.sql_mode -- 将 ONLY_FULL_GROUP_BY 去掉 set @@global.sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
设置完后，如果不生效，可以退出重新登录
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