PostgreSQL value of COUNT multiply by a number - sql

Question

I'm a Rails developer and I'm new to writing SQL script. I have users, portfolios, views, favorites and endorsements tables. users have many portfolios and many endorsements.portfolioshas manyviews, manyfavoritesand manyendorsements`.
Here is the script I wrote
top_users = User.find_by_sql(
"SELECT users.*,
COUNT(portfolios.id) +
COUNT(views.id) +
COUNT(favorites.id) +
COUNT(case when endorsements.portfolio_id = portfolios.id AND portfolios.user_id = users.id then 1 else 0 end) +
COUNT(case when endorsements.user_id = users.id then 1 else 0 end)
AS total
FROM users
LEFT OUTER JOIN portfolios ON portfolios.user_id = users.id
LEFT OUTER JOIN views ON views.subject_id = portfolios.id AND portfolios.user_id = users.id
LEFT OUTER JOIN favorites ON favorites.subject_id = portfolios.id AND portfolios.user_id = users.id
LEFT OUTER JOIN endorsements ON endorsements.portfolio_id = portfolios.id AND portfolios.user_id = users.id OR endorsements.user_id = users.id
GROUP BY users.id
ORDER BY total DESC LIMIT 8"
)
total count is not fully what I expect because each portfolio is worth 50 points, view is 2 points, favorite is worth 10 points, and endorsement is worth 2 points.
Let say we have 3 users
user | COUNT 1 | COUNT 2 | COUNT 3 | COUNT 4 | COUNT 5
-------------------------------------------------------
1 | 0 | 0 | 0 | 0 | 10
2 | 2 | 2 | 2 | 2 | 0
3 | 5 | 0 | 0 | 0 | 0
With my script, the result come in the order of user 1, user 2, then users 3. However base on the points system, it should come out in the order of user 3, user 2 then user 1 because user 3 total points is 250, users 2 total is 128 and user 1 is 20, and this is the order I expect. I did tried this:
top_users = User.find_by_sql(
"SELECT users.*,
COUNT(portfolios.id) * 50 +
COUNT(views.id) * 2 +
COUNT(favorites.id) * 10 +
COUNT(case when endorsements.portfolio_id = portfolios.id AND portfolios.user_id = users.id then 1 else 0 end) * 2 +
COUNT(case when endorsements.user_id = users.id then 1 else 0 end) * 2
AS total
FROM users
LEFT OUTER JOIN portfolios ON portfolios.user_id = users.id
LEFT OUTER JOIN views ON views.subject_id = portfolios.id AND portfolios.user_id = users.id
LEFT OUTER JOIN favorites ON favorites.subject_id = portfolios.id AND portfolios.user_id = users.id
LEFT OUTER JOIN endorsements ON endorsements.portfolio_id = portfolios.id AND portfolios.user_id = users.id OR endorsements.user_id = users.id
GROUP BY users.id
ORDER BY total DESC LIMIT 8"
)
I tried the above script but does not work for me. Any thoughts or help would be much appreciated. Again, I'm very new with raw SQL script.
UPDATED
I ended up doing this to avoid double count issue when LEFT INNTER JOIN multiple table.
SELECT t4.id, t4.username, t4.avatar_url, p_count * 50 + ue_count * 2 + fav_count * 10 + ep_count * 2 + COUNT(vp.id) * 2 as point
FROM (SELECT t3.id, t3.username, t3.avatar_url, p_count, ue_count, fav_count, COUNT(ep.id) as ep_count
FROM( SELECT t2.id, t2.username, t2.avatar_url, p_count, ue_count, COUNT(fav_p.id) as fav_count
FROM (SELECT t1.id, t1.username, t1.avatar_url, p_count, COUNT(e.user_id) as ue_count
FROM (SELECT u.*, COUNT(p.user_id) as p_count
FROM users u
LEFT OUTER JOIN (SELECT user_id, id
FROM portfolios) p
ON u.id = p.user_id
GROUP BY u.id) t1
LEFT OUTER JOIN (SELECT user_id
FROM endorsements) e
ON e.user_id = t1.id
GROUP BY t1.id, t1.username, t1.avatar_url, p_count ) t2
LEFT OUTER JOIN (SELECT p.id, p.user_id
FROM portfolios p
INNER JOIN favorites
ON favorites.subject_id = p.id) fav_p
ON fav_p.user_id = t2.id
GROUP BY t2.id, t2.username, t2.avatar_url, p_count, ue_count) t3
LEFT OUTER JOIN (SELECT p.id, p.user_id
FROM portfolios p
INNER JOIN endorsements
ON endorsements.portfolio_id = p.id) ep
ON ep.user_id = t3.id
GROUP BY t3.id, t3.username, t3.avatar_url, p_count, ue_count, fav_count) t4
LEFT OUTER JOIN (SELECT p.id, p.user_id
FROM portfolios p
INNER JOIN views
ON views.subject_id = p.id) vp
ON vp.user_id = t4.id
GROUP BY t4.id, t4.username, t4.avatar_url, p_count, ue_count, fav_count, ep_count
ORDER BY point DESC
LIMIT 8
Since I'm not familiar with SQL script as I'm a very beginner. The updated code above solve my problem but I wonder how bad the performance would be if I do that. Thanks for any inputs.

Answer 1

After reading through a few more times, I think I got what you were saying. Try this.
SELECT users.id
,COUNT(portfolios.id) * 50 +
COUNT(VIEWS.id) * 2 +
COUNT(favorites.id) * 10 +
COUNT(e1.id) * 2 +
COUNT(e2.id) * 2
AS total
FROM users
LEFT JOIN portfolios
ON portfolios.user_id = users.id
LEFT JOIN VIEWS
ON VIEWS.subject_id = portfolios.id
LEFT JOIN favorites
ON favorites.subject_id = portfolios.id
LEFT JOIN endorsements e1
ON e1.portfolio_id = portfolios.id
LEFT JOIN endorsements e2
ON e2.user_id = users.id
GROUP BY users.id
ORDER BY total DESC LIMIT 8
I assumed that endorsements related to either a user OR a portfolio. I don't know what your values look like in your tables but in theory, since an endorsement relates to a user or a portfolio but a portfolio always relates to a user it wouldn't be strictly necessary to join on both user_id or portfolio_id. In a case like that it's find to join the users table to the endorsements as e1 and the portfolios table to the endorsements as e2 and just add them.

Answer 2

First of all, unless your 'users" table only has one column, this breaks the rule that when you have aggregate functions in your select clause, every column that isn't passed into an aggregate function, has to be in your group by clause.
Second I don't think the case statements inside your COUNT() functions make sense. They are the same statements in your join. You should be able to just count the endoresements.Id and the Portfolios.id, I think. I may be a little fuzzy on what you're looking for. Also, what is a subject_id? is that an id field that determines whether an endorsement belongs to a user or a portfolio?
does a portfolio have both a user_id and a portfolio_id or is it one or the other but not both?

Answer 3

Any time you have multiple outer joins in a GROUP BY query, you have to be careful of double-counting. So I would change COUNT(portfolios.id) to COUNT(DISTINCT portfolios.id) etc. That should also remove the need for your CASE statements. Once you have those counts, you can multiply by their score values, as you say in your question (* 2 or * 50 or whatever you like).