find count of read and unread posts given userid and courseid

gistfile1.sql

SELECT d.id AS discussion,
f.name AS name,
sum(case when r.postid is null then 1 else 0 end) as unread_posts,
sum(case when r.postid is null then 0 else 1 end) as read_posts
FROM mdl_course c
JOIN mdl_forum_discussions d on d.course = c.id
JOIN mdl_forum f on f.id = d.forum
JOIN mdl_forum_posts p ON p.discussion = d.id
LEFT JOIN mdl_forum_read r ON r.postid = p.id
WHERE c.id = 3
and r.userid=4
group by d.id, f.name;