Энштеин, Если я правильно понял, то вот запрос с джоином
SELECT COUNT(c.msg) AS counter, p.post, p.user_id, p.id, u.name FROM posts AS p LEFT JOIN comments AS c LEFT JOIN users AS u ON u.id = p.user_id AND c.post_id = p.id
Энштеин, Если я правильно понял, то вот запрос с джоином
SELECT COUNT(c.msg) AS counter, p.post, p.user_id, p.id, u.name FROM posts AS p LEFT JOIN comments AS c LEFT JOIN users AS u ON u.id = p.user_id AND c.post_id = p.id