根据子查询中的计数显示表结果

Question

This is really doing my head in, it be a simple query I thought.

blog table:

blog_id
blog_name
blog_copy

comments table:

comment_id
comment_copy
comment_by
blog_id

I want to show blog items where there are more than 3 comments and also order them by the volume of replies.

I tried many queries including this but it just doesn't work:

SELECT 
    *, blog_id as BID , 
    (SELECT blog_id 
     FROM comments 
     WHERE blog = BID HAVING COUNT(*) > 3) AS t2
FROM blog
WHERE mostcomments > '3'
ORDER by mostcomments ASC

It says that mostcomments doesn't exist. I've done it other ways and it executes but counts comments on totals overall not per blog_id it's looking up

Answer 1

You need to use GROUP BY :

select b.blog_id, count(*)
from blog b
  join comments c on b.blog_id = c.blog_id
group by b.blog_id
having count(*) > 2 
order by count(*) desc

• SQL Fiddle Demo