MySQL query order by multiple items

Is it possible to order by multiple rows?

I want my users to be sorted by last_activity, but at the same time, I want the users with pictures to appear before the ones without

Something like this:

SELECT some_cols
FROM `prefix_users`
WHERE (some condi开发者_开发问答tions)
ORDER BY last_activity, pic_set DESC;

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

Note that we can place ASC or DESC after each column (like above does for pic_set), or leave it to default (like above's last_activity-column).

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Sort by picture and then by activity:

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

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