来自codeigniter的重复数据左连接

Question

SELECT *
FROM `tbl_schedule_task` AS `E`
JOIN `tbl_schedule` AS `S` ON `S`.`schedule_id`=`E`.`schedule_id`
JOIN `tbl_schedule_frequency` AS `F` ON `F`.`frequency_id`=`S`.`frequency_id`
JOIN `tbl_equipments` AS `M` ON `M`.`equipment_id`=`E`.`equipment_id`
LEFT JOIN `tbl_schedule_checklist` AS `L` ON `L`.`check_list_id`=`E`.`check_list_id`
LEFT JOIN `tbl_tech_groups` AS `G` ON `G`.`group_id` = `S`.`shedule_assign_id`
LEFT JOIN `tbl_tech_technicians` AS `T` ON `T`.`techgroup_id`=`G`.`group_id`
LEFT JOIN `tbl_schedule_category` AS `SC` ON `SC`.`category_id`=`S`.`category_id`
JOIN `tbl_site_users` AS `U` ON `U`.`user_id`=`E`.`created_by`
WHERE `E`.`site_id` = '1'
  AND (`E`.`approve_flg` =0
       AND `E`.`check_out` = 1)
  AND `E`.`approve_by` = '2'
ORDER BY `E`.`task_id` DESC

Answer 1

可能是内连接正在返回重复数据。在上面查询的左连接之前检查内连接。