mysql多个项目的查询顺序

是可以通过多行进行sorting？

我希望我的用户按last_activity进行sorting，但是同时我希望带有图片的用户在没有图片的情况下出现

像这样的东西：

SELECT some_cols FROM `prefix_users` WHERE (some conditions) ORDER BY last_activity, pic_set DESC; 

Answer 1

 SELECT some_cols FROM prefix_users WHERE (some conditions) ORDER BY pic_set DESC, last_activity; 

Answer 2

按照图片sorting，然后按照活动sorting：

 SELECT some_cols FROM `prefix_users` WHERE (some conditions) ORDER BY pic_set, last_activity DESC; 

Answer 3

 SELECT id, user_id, video_name FROM sa_created_videos ORDER BY LENGTH(id) ASC, LENGTH(user_id) DESC