Join 4 tables with group by, 2 having and where clause - postgresql

Question

I have the database consists of 4 tables:
users(id, "name", surname, birthdate)
friendships(userid1, userid2, "timestamp")
posts(id, userid, "text", "timestamp")
likes(postid, userid, "timestamp")
I need to get a result set of unique usernames having more than 3 friendships within January of 2018 and their "likes" average per "post" in the range of [10; 35).
I wrote this statement for the first step:
select distinct u."name"
from users u
join friendships f on u.id = f.userid1
where f."timestamp" between '2018-01-01'::timestamp and '2018-01-31'::timestamp
group by u.id
having count(f.userid1) > 3;
It's working fine and returns 3 rows. But when I'm adding the second part this way:
select distinct u."name"
from users u
join friendships f on u.id = f.userid1
join posts p on p.userid = u.id
join likes l on p.id = l.postid
where f."timestamp" between '2018-01-01'::timestamp and '2018-01-31'::timestamp
group by u.id
having count(f.userid1) > 3
and ((count(l.postid) / count(distinct l.postid)) >= 10
and (count(l.postid) / count(distinct l.postid)) < 35);
I'm getting crazy 94 rows. I don't know why.
Will be thankful for possible help.

Answer 1

You don't need distinct in u.name because aggregate will remove the duplicate.
select
u."name"
from
users u
inner join friendships f on u.id = f.userid1
inner join posts p on u.id = p.userid
inner join likes l on p.id = l.postid
where
f."timestamp" >= '2018-01-01'::timestamp
and f."timestamp" < '2018-02-01'::timestamp
group by
u."name"
having
count(distinct f.userid1) > 3
and ((count(l.postid) / count(distinct l.postid)) >= 10
and (count(l.postid) / count(distinct l.postid)) < 35);
As in comment stated. Not good idea when you use between for date to do range.
f."timestamp" >= '2018-01-01'::timestamp
and f."timestamp" < '2018-02-01'::timestamp
Will give you a full month of January.

Answer 2

Try the below! The issue with using "count(f.userid1) > 3" is that if a user has , e.g. 2 friends and 6 posts and 3 likes they'll get 2 x 6 = 12 rows, so 12 records with non-null f.userid1. By counting distinct f.userid2 you can count distinct friends. Similar issues appear for the other counts used for filtering.
select u."name"
from users u
join friendships f on u.id = f.userid1
join posts p on p.userid = u.id
left join likes l on p.id = l.postid
where f."timestamp" > '2018-01-01'::timestamp and f."timestamp" < '2018-02-01'::timestamp
group by u.id, u."name"
having
--at least three distinct friends
count( distinct f.userid2) > 3
--distinct likes / distinct posts
--we use l.* to count distinct likes since there's no primary key
and ((count(distinct l.*) / count(distinct p.id)) >= 10
and ((count(distinct l.*) / count(distinct p.id)) < 35);