I needed a result with Group By three columns and the SQL works perfectly without any issue. I'm facing the issue when I use it in the CodeIgniter framework; it doesn't execute the query. My Code and SQL are as follows.
Code
$this->db->select(['trk.userid AS user_id', 'scr.course AS course_id'])
->from('mdl_scorm scr')
->join('mdl_scorm_scoes_track trk', 'scr.id = trk.scormid', 'inner')
->join('mdl_course_modules mcs', 'mcs.instance = scr.id', 'inner')
->where_in('trk.value', ['completed','incomplete','passed'])
->group_by(['scr.course', 'trk.userid', 'trk.scormid'])
->order_by('trk.userid', 'DESC');
SQL
SELECT `trk`.`userid` AS user_id, `scr`.`course` AS course_id
FROM (`mdl_scorm` scr)
INNER JOIN `mdl_scorm_scoes_track` trk ON `scr`.`id` = `trk`.`scormid` INNER JOIN `mdl_course_modules` mcs ON `mcs`.`instance` = `scr`.`id`
WHERE `trk`.`value` IN ('completed', 'incomplete', 'passed')
GROUP BY `scr`.`course`, `trk`.`userid`, `trk`.`scormid`
ORDER BY `trk`.`userid` DESC LIMIT 0,100;
This works fine when the group_by has only two columns, like,
->group_by(['scr.course', 'trk.userid'])
What could be the reason?