[Err] 1055 - Expression＃2 of select list is not in GROUP BY clause and contains nonaggregated column

stay MySQL Use group by Report errors ：

select courseid,score,stuid from score group by courseid;

[Err] 1055 - Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'ssm.score.stuid' 
which is not functionally dependent on columns in GROUP BY clause; 
this is incompatible with sql_mode=only_full_group_by

select The field of appears group by Fields that do not appear in , So wrong reporting ; stay sql_mode=only_full_group_by when , The following expressions are allowed ：

select a,b [ Aggregate functions (c)] from table_name group by a,b

 In this column ：group by  Yes 2 A field ：a, b; therefore select Legal writing of fields ：
select a [ Aggregate functions (c)] /select b [ Aggregate functions (c)] /select a,b [ Aggregate functions (c)] 

If you want to select Fields are not subject to group by The field limit only needs to be set sql_mode that will do ;

1. Find out sql_mode  Value 
select @@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
 Copy values , Different versions sql_mode The value of may not be the same , Just copy the value according to your own query 
2. take ONLY_FULL_GROUP_BY Get rid of , To reset sql_mode Value 
set global sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
 

This method is restarting MySQL after , It will still return to the previous mode ; Want permanent effect , You need to use the following method ： stay ini Add... To the file ：

[mysqld]
sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'