mysql 5.7以上版本 group by问题

安装了mysql8.0，用group by 查询时抛出如下异常：

Expression #3 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'userinfo.t_long.user_name' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

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原因：

      MySQL 5.7.5和up实现了对功能依赖的检测。如果启用了only_full_group_by SQL模式(在默认情况下是这样)，那么MySQL就会拒绝选择列表、条件或顺序列表引用的查询，这些查询将引用组中未命名的非聚合列，而不是在功能上依赖于它们。(在5.7.5之前，MySQL没有检测到功能依赖项，only_full_group_by在默认情况下是不启用的。关于前5.7.5行为的描述，请参阅MySQL 5.6参考手册。)

执行以下个命令，可以查看 sql_mode 的内容。

mysql> SHOW SESSION VARIABLES;

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mysql> SHOW GLOBAL VARIABLES;

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mysql> select @@sql_mode;

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可见session和global 的sql_mode的值都为： 
ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

only_full_group_by说明： 
only_full_group_by ：使用这个就是使用和oracle一样的group 规则, select的列都要在group中,或者本身是聚合列(SUM,AVG,MAX,MIN) 才行，其实这个配置目前个人感觉和distinct差不多的，所以去掉就好 
官网摘抄： 
官网：ONLY_FULL_GROUP_BY 
Reject queries for which the select list, HAVING condition, or ORDER BY list refer to nonaggregated columns that are neither named in the GROUP BY clause nor are functionally dependent on (uniquely determined by) GROUP BY columns.

As of MySQL 5.7.5, the default SQL mode includes ONLY_FULL_GROUP_BY. (Before 5.7.5, MySQL does not detect functional dependency and ONLY_FULL_GROUP_BY is not enabled by default. For a description of pre-5.7.5 behavior, see the MySQL 5.6 Reference Manual.)

A MySQL extension to standard SQL permits references in the HAVING clause to aliased expressions in the select list. Before MySQL 5.7.5, enabling ONLY_FULL_GROUP_BY disables this extension, thus requiring the HAVING clause to be written using unaliased expressions. As of MySQL 5.7.5, this restriction is lifted so that the HAVING clause can refer to aliases regardless of whether ONLY_FULL_GROUP_BY is enabled.

解决：

执行以下两个命令：

mysql> set global sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';

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mysql> set session sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';

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这两个命令，去掉 sql_mode 的 ONLY_FULL_GROUP_BY