SQL - How To Order Using Count From Another Table

Question

1. Bloggers

blogger_id
1 
2
3

2. Posts

post_from_blogger_id
1 
1
1
2
2
3

As

Answer 1

 SELECT bloggers.*, COUNT(post_id) AS post_count
    FROM bloggers LEFT JOIN blogger_posts 
    ON bloggers.blogger_id = blogger_posts.blogger_id
    GROUP BY bloggers.blogger_id
    ORDER BY post_count

(Note: MySQL has special syntax that lets you GROUP BY without aggregating all values, it's intended for exactly this situation).