MySQL 报错 1055

[2019-02-20 11:57:36] [42000][1055] Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column ‘exer.student.sid‘ which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

select version(),
@@sql_mode;SET sql_mode=(SELECT REPLACE(@@sql_mode,‘ONLY_FULL_GROUP_BY‘,‘‘));

show variables like "sql_mode";
set sql_mode=‘‘;
set sql_mode=‘NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES‘;