Question

I have three tables. Categories, topics, and posts. Each topic has a foreign key that references the category that it’s under. Each post has a foreign key that references the topic that it’s under.

The purpose of this query is to basically be the front page query. I want each category along with the number of topics and number of posts in each category. This is the query I have, and it works. Is this the simplest way of going about it?

SELECT      c.*,
            COUNT(t.idCategory) AS tCount,
            p.pCount
FROM        categories AS c
  LEFT JOIN topics AS t
  ON        c.id = t.idCategory
  LEFT JOIN (SELECT      t.idCategory,
                         COUNT(p2.idTopic) AS pCount
             FROM        topics AS t
               LEFT JOIN posts AS p2
               ON        t.id = p2.idTopic
             GROUP BY    t.idCategory) AS p
  ON         c.id = p.idCategory
GROUP BY     t.idCategory
ORDER BY     c.id

Thanks!

Answer 1

If you are talking of simplicity I guess this could be an answer:

Select 
      c.*,
      (Select count(*) from topic t where c.id = t.idCategory) as tCount,
      (Select count(*) from posts p join topics t2 on t2.id = p.idTopic where c.id = t2.idCategory) as pCount
From categories c