1. group by语句问题
问题：
SQL 错误 [1055] [42000]: Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'pymysql.users.password' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
解决：
ONLY_FULL_GROUP_BY：
对于GROUP BY聚合操作，若select中的列没有在group by中出现，那么这句SQL是不合法的。
解决办法下my.cnf中添加以下几行
<pre>[mysqld]
sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'
