【问题解决】【sql_mode不兼容】incompatible with sql_mode=only_full_group_by

String sql="select *,count(groupName) as isNum,'Y' as isMark from t_pm_projecttemplate group by groupName order by groupName ";

上述SQL语句报错如下：

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'zjrxmis.t_pm_projecttemplate.id' 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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原因是什么呢？简单的讲就是select查询的列不包含在group by的列中；

深入分析原因：

已知我的mysql版本如下，

only_full_group_by 的意思是：对于GROUP BY聚合操作，如果在SELECT中的列，没有在GROUP BY中出现，那么这个SQL是不合法的，因为列不在GROUP BY从句中，也就是说查出来的列必须在group by后面出现否则就会报错，或者这个字段出现在聚合函数里面。其实这个配置感觉和distinct差不多的，所以去掉就好 

命令行输入：

set @@GLOBAL.sql_mode='';

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

默认关掉ONLY_FULL_GROUP_BY！

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这个时候再用select 一下，

SELECT @@sql_mode;

SELECT @@GLOBAL.sql_mode;

发现已经不存在ONLY_FULL_GROUP_BY ，感觉已经OK。但是如果你重启Mysql服务的话，发现ONLY_FULL_GROUP_BY还是会存在的！

发现已经不存在ONLY_FULL_GROUP_BY ，感觉已经OK。但是如果你重启Mysql服务的话，发现ONLY_FULL_GROUP_BY还是会存在的！

发现已经不存在ONLY_FULL_GROUP_BY ，感觉已经OK。但是如果你重启Mysql服务的话，发现ONLY_FULL_GROUP_BY还是会存在的！

 所以想要彻底解决修改mysql配置文件：

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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2018年12月13日14:22:42补充

注意：

1.修改完配置文件后，记得重启mysql服务，可以去任务管理器哪里重启，也可以用命令，如果不会，那就重启电脑吧；

2.如果你们mysql安装路径没有这个文件，就把my-default.ini 改成my.ini，我这个版本5.7.17就是没有my.ini配置问题）；

如果遇到mysql服务无法启动的话，那大概是配置文件错了，可以参考如下：

# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html
# *** DO NOT EDIT THIS FILE. It's a template which will be copied to the
# *** default location during install, and will be replaced if you
# *** upgrade to a newer version of MySQL.

[mysqld]

# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M

# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin

# These are commonly set, remove the # and set as required.
# basedir = .....
# datadir = .....
# port = .....
# server_id = .....


# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M 

sql_mode = STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION