SQL执行错误: SELECT * FROM `CourseRel` `CourseRel` GROUP BY `LessonId`
错误代码: 1055
错误信息: Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'jiluai.CourseRel.CourseId' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by