Question

This is really a head scratcher for me. Essentially I have 3 MySQL tables that collectively keep track of someone’s score (for a game let’s say). New scores can always be input. Essentially what I need to figure out is what players have improved their score from the past week (for this, they need to have a score before the week started AND after). Here is my table layout:

   USER                   REQUEST (ASSOCIATIVE TABLE)                   SCORE
+----------+    +-----------------------------------------+       +--------------------+
| id (int) |    | id  |    user_id   |    date (UNIX TS)  |       | request_id | score |
+----------+    +-----------------------------------------+       +--------------------+
|    3     |    |  1  |      3       |    before week     |       |     1      |  10   |
|    4     |    |  2  |      3       |    after week      |       |     2      |  20   |
|    5     |    |  3  |      4       |    before week     |       |     3      |  5    |
+----------+    |  4  |      5       |    after week      |       |     4      |  15   |
                +-----------------------------------------+       +--------------------+

So essentially, from those tables, I want to have user with ID of 3 to be returned because he’s the only one that has improved his score this last week.

So far, this is where I’ve come to but I really am having trouble moving forward:

SELECT user.id AS user_id, score, count(*) AS n 
FROM user 
LEFT JOIN request ON request.user_id = user.id 
LEFT JOIN score ON score.request_id = request.id WHERE request.date > (WEEK UNIX TS) 
GROUP BY user_id HAVING n > 1 
ORDER BY request.date DESC

Thanks for your help! 🙂

Answer 1

SELECT user.id             AS user_id
     , MAX(sc_now.score)   AS score_now
     , MAX(sc_prev.score)  AS score_previous

FROM user 

  JOIN request AS req_now
    ON  req_now.user_id = user.id 
    AND req_now.date > (WEEK UNIX TS)    --- condition for this week 
  JOIN score AS sc_now
    ON sc_now.request_id = req_now.id 

  JOIN request AS req_prev
    ON  req_prev.user_id = user.id 
    AND req_prev.date BETWEEN ? AND ?    --- condition for previous week
  JOIN score AS sc_prev
    ON sc_prev.request_id = req_prev.id 

GROUP BY user.id

HAVING MAX(sc_now.score) > MAX(sc_prev.score)