SQL schema Site Leader Board - sql

Question

So I am trying to set up a site which has challenges and then want to convert that to leader boards for each challenge, and then an all time leaderboard.
So I have a challenges table that looks like this:
Challenge ID Challenge Name Challenge Date Sport Prize Pool
Then I need a way so each challenge has its own leader board of say 50 people.
linked by the challenge ID where that will = Leaderboard ID
I have a leader board of 50 people for that challenge that will look something like this:
Challenge ID User Place Prize Won
My question is 2 things:
How can I make a table auto create when a new challenge is added to the challenges table?
How can I get an A site wide leader board for every challenge so it will show the following:
Rank USER Prize Money Won(total every challenge placed)
and then base rank order by how much money won..
I know this is a lot of questions all wrapped in one, schema design and logic.
Any insights greatly appreciated

Answer 1

A better approach than one table per challenge is one table for all of them. That way you can compute grand totals and individual challenge rankings all with the same table. You'd also want to not record the place directly but compute it on the fly with the appropriate window function depending on how you want to handle ties (rank(), dense_rank(), and row_number() will have different results in those cases); that way you don't have to keep adjusting it as you add new records.
A table something like (You didn't specify a SQL database, so I'm going to assume Sqlite. Adjust as needed.):
CREATE TABLE challenge_scores(user_id INTEGER REFERENCES users(id),
challenge_id INTEGER REFERENCES challenges(id),
prize_amount NUMERIC,
PRIMARY KEY(user_id, challenge_id));
will let you do things like
SELECT *
FROM (SELECT user_id,
sum(prize_amount) AS total,
rank() OVER (ORDER BY sum(prize_amount) DESC) AS place
FROM challenge_scores
GROUP BY user_id)
WHERE place <= 50
ORDER BY place;
for the global leaderboard, or the similar:
SELECT *
FROM (SELECT user_id,
prize_amount,
rank() OVER (ORDER BY prize_amount DESC) AS place
FROM challenge_scores
WHERE challenge_id = :some_challenge_id
GROUP BY user_id)
WHERE place <= 50
ORDER BY place;
for a specific challenge's.