Displaying a single rank in MySQL table

Question

I have a table called 'highscores' that looks like this.

id      udid       name       score
1       1111       Mike       200
2       3333       Joe        300
3       4444       Billy      50
4       0000       Loser      10
5       DDDD       Face       400

Given a specific udid, I want to return the rank of that row by their score value.

i.e. if udid given = 0000, I should return 5.

Any idea how to write this query for a MySQL database?

Answer 1

MySQL doesn't have any analytic/ranking functionality, but you can use a variable to artificially create a rank value:

  SELECT t.id,
         t.udid,
         t.name,
         t.score,
         @rownum := @rownum + 1 AS rank
    FROM HIGHSCORES t
    JOIN (SELECT @rownum := 0) r
ORDER BY t.score DESC

In order to see what rank is associated with UDID "0000", use:

SELECT MAX(x.rank) AS rank
  FROM (SELECT t.id,
               t.udid,
               t.name,
               t.score,
               @rownum := @rownum + 1 AS rank
          FROM HIGHSCORES t
          JOIN (SELECT @rownum := 0) r
      ORDER BY t.score DESC) x
 WHERE x.udid = '0000'

Need the MAX for if the user has multiple high score values. Alternately, you could not use MAX and use ORDER BY rank LIMIT 1.

Answer 2

To reiterate OMG's excellent answer which is the general case of multiple high scores per udid, here's the query based on the precondition of exactly one entry per udid:

SELECT rank
FROM
   (SELECT @rownum := @rownum + 1 AS rank, score, udid
    FROM highscores
    JOIN (SELECT @rownum := 0) r
    ORDER BY highscores.score DESC) x
WHERE x.udid = '0000'