Question

tables:
POSTS
(id
title
data
userid)

CONNECTIONS(
postid
userid)

I want to get rows from the POSTS table by the amount of c.postid values that are the same in the CONENCTIONS c table

In easier terms, I want to get the most popular posts, with the most connections.

I hope that makes sense.

Answer 1

SELECT p.id, p.name, c.cnt from posts p INNER JOIN (
    SELECT postid, count(*) as cnt 
    FROM connections 
    GROUP BY postid ORDER BY cnt DESC /*limit goes here if you need it!*/) c 
ON c.postid = p.id

A little warning:

It would be pretty heavy query in case if you dealing with high loads. I’d suggest to have the cnt (a number of connections) field right within your posts table (it would be a denormalization and it’s harder to maintain, but would work good enough to decrease querying time by 2 times or more if you would create an index on cnt field).

Let me know if the query has worked or not, cause I can’t check myself right now.