mysql之group_by

背景：等级除了会员本身等级外，还有课程分类，课程分类可以添加多条分佣的比例，按照目前生效的时间以及最大id获取到全部分佣，然后再提取自己想要的数据显示。

目标需求：

实现代码：

SELECT ml.*FROM ims_tycb_xyl_member_level_commission ml

INNER JOIN (SELECT id,MAX(start_time) as start_time FROM ims_tycb_xyl_member_level_commission

where start_time < unix_timestamp()

GROUP BY id ORDER BY id DESC ) m

on m.id = ml.id and m.start_time=ml.start_time AND ml.level_id=19

GROUP BY ml.commission_type ORDER BY ml.id DESC,start_time DESC