Mysql 错误“1055”

<center><font size='5' color='#fff'>错误“1055”</font></center>

• 错误

  mysql>SELECT * FROM `user_resource`
        WHERE (1=1) GROUP BY CouId,UsrId ORDER BY CouId asc LIMIT 10 OFFSET 0 ;
  

  出错：

  ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause 
  and contains nonaggregated column 'eascs_eatp.user_resource.ResId' which is not functionally 
  dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
  

• 原因

  问题原因： 
  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。 
  
  在MySQL5.7之后，sql_mode中默认存在ONLY_FULL_GROUP_BY，
  SQL语句未通过ONLY_FULL_GROUP_BY语义检查所以报错。
  

• 解决方法1[^该方法是短期的，退出Mysql操作后失效，永久实现参考方法2]

查询sql_mode

第一项默认开启ONLY_FULL_GROUP_BY了,导致出现了错误,需要把它的默认关掉。

mysql> SELECT @@GLOBAL.sql_mode;
+-----------------------------------------------------------------------------------------------------------------------+
| @@GLOBAL.sql_mode                                                                                                     |
+-----------------------------------------------------------------------------------------------------------------------+
| ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION |
+-----------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

删除（重新设置）:

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

Query OK, 0 rows affected (0.01 sec)

• 重新查询

  mysql> SELECT @@GLOBAL.sql_mode;
  +-----------------------------------------------------------------------------------------------------------------------+
  | @@GLOBAL.sql_mode                                                                                                     |
  +-----------------------------------------------------------------------------------------------------------------------+
  | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION |
  +-----------------------------------------------------------------------------------------------------------------------+
  1 row in set (0.00 sec)
  
  mysql> set sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
  Query OK, 0 rows affected (0.01 sec)
  
  mysql> SELECT * FROM `user_resource`  WHERE (1=1) GROUP BY CouId,UsrId ORDER BY CouId asc LIMIT 10 OFFSET 0;
  +-------+-----------+----------+-------------+---------------------+---------------------+-------+
  | UsrId | ResId     | CouId    | CanDownload | ExpTime             | AddTime             | AccId |
  +-------+-----------+----------+-------------+---------------------+---------------------+-------+
  |   667 | 324243746 | cxcy     |           9 | 2020-03-02 16:55:00 | 2020-03-02 16:55:00 | admin |
  |   667 | 324243645 | gyldsj   |           9 | 2020-03-02 16:56:00 | 2020-03-02 16:56:00 | admin |
  |   667 | 324243449 | gyljr    |           9 | 2020-03-02 16:56:00 | 2020-03-02 16:56:00 | admin |
  |   667 | 324243547 | gyljwlgl |           9 | 2020-03-02 16:56:00 | 2020-03-02 16:56:00 | admin |
  |   667 | 324243718 | xls      |           9 | 2020-03-02 16:57:00 | 2020-03-02 16:57:00 | admin |
  +-------+-----------+----------+-------------+---------------------+---------------------+-------+
  5 rows in set (0.00 sec)
  

• 解决方法2[^永久]

  进入mysql查询sql_mode

    mysql> SELECT @@GLOBAL.sql_mode;
    +-----------------------------------------------------------------------------------------------------------------------+
    | @@GLOBAL.sql_mode                                                                                                     |
    +-----------------------------------------------------------------------------------------------------------------------+
    | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION |
    +-----------------------------------------------------------------------------------------------------------------------+
    1 row in set (0.00 sec)
    
  

  复制然后去除ONLY_FULL_GROUP_BY,如下：

  sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION

  linux环境下，vim到my.cnf（我的my.cnf是 cd /etc）

  #添加刚刚复制的代码
  sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,
      NO_ENGINE_SUBSTITUTION 
  

  重启服务器:

  service mysqld restart