Ranking in MySQL - php

Question

Currently I am developing a system to support a competition. In this competition there are 11 judges that give a grade to the participant. This grade is stored in a table per judge. With the following Select statement I retrieve the total score from the MySQL database (and also some inner joins to select other information from other tables).
Now I want to have ranking in this system, where also ex aequo is taken into account. I have tried several mysql solutions from this forum. But somehow the statement is always incorrect. Hopefully, someone can help me.
SELECT optreden.id, optreden.wedstrijd, optreden.jaartal,
liedje.titel, club.volledige_clubnaam,
(SELECT SUM(score.score_lied) FROM score WHERE score.optreden=optreden.id) AS score
FROM optreden
INNER JOIN liedje ON optreden.liedje=liedje.id
INNER JOIN club ON liedje.uitvoerende_club=club.id
WHERE optreden.wedstrijd="voorselectie" AND optreden.jaartal=2014
GROUP BY optreden.id
ORDER BY score_lied DESC
With this query, I get the following result:
+----+--------------+------+----------+--------------+------+
| id | Competition | Year | Title | Artist (club)| Score|
+----+--------------+------+----------+--------------+------+
| 12 | voorselectie | 2014 | Song 1 | Club 1 | 792 |
| 16 | voorselectie | 2014 | Song 2 | Club 2 | 600 |
| 10 | voorselectie | 2014 | Song 3 | Club 3 | 600 |
| 11 | voorselectie | 2014 | Song 3 | Club 3 | 500 |
| 12 | voorselectie | 2014 | Song 3 | Club 3 | 400 |
The query fetches information from the following tables:
Score: in this table the scores given by the 11 judges is stored as
line-items (result is given below);
Optreden: in this table the information from the club and the song is linked;
Club: information from the club,
such as name;
Liedje: information about the song, performed by the
club.
All the tables are linked by id's. In the result, there should come a column, with the ranking of the club.
The result from the table score is as follows:
+----+----+--------+----+
| ID | Pid| Userid | 85 |
+----+----+--------+----+
| 1 | 12 | 444 | 85 |
| 12 | 12 | 454 | 92 |
| 13 | 12 | 445 | 87 |
| 14 | 12 | 446 | 56 |
| 15 | 12 | 447 | 81 |
| 16 | 12 | 448 | 78 |
| 17 | 12 | 449 | 55 |
| 18 | 12 | 450 | 69 |
| 19 | 12 | 451 | 88 |
| 20 | 12 | 452 | 69 |
| 21 | 12 | 453 | 32 |
+----+----+--------+----+
Where the columns represent the following:
- ID: the id of the score in the table;
- Pid: the id of the performance (with this performing club and song are linked);
- Userid: the userid of the 11 judges;
- Score: the score given by each judge.
The end result should be as follows:
+----+--------------+------+----------+--------------+------+------+
| id | Competition | Year | Title | Artist (club)| Score| Rank |
+----+--------------+------+----------+--------------+------+------+
| 12 | voorselectie | 2014 | Song 1 | Club 1 | 792 | 1 |
| 16 | voorselectie | 2014 | Song 2 | Club 2 | 600 | 2 |
| 10 | voorselectie | 2014 | Song 3 | Club 3 | 600 | 2 |
| 11 | voorselectie | 2014 | Song 3 | Club 3 | 500 | 4 |
| 12 | voorselectie | 2014 | Song 3 | Club 3 | 400 | 5 |
I have tried the solution from Neville before and now again. I have rewritten the SQL statement as follows:
SELECT optreden.id, optreden.wedstrijd, optreden.jaartal,
liedje.titel, club.volledige_clubnaam,
(SELECT SUM(score.score_lied) FROM score WHERE score.optreden=optreden.id) AS score, CASE
WHEN #prev_value = score THEN #rank_count
WHEN #prev_value := score THEN #rank_count := #rank_count + 1
END AS rank,
FROM optreden
INNER JOIN liedje ON optreden.liedje=liedje.id
INNER JOIN club ON liedje.uitvoerende_club=club.id
WHERE optreden.wedstrijd="voorselectie" AND optreden.jaartal=2014
GROUP BY optreden.id
ORDER BY score_lied DESC
Here I get the error: Unknown column 'score' in 'field list'..

Answer 1

It seems that you are getting this error simply because there is no field score... I have extracted your inner SELECT into a JOIN so the real field can be used directly. (Not tested though, sorry)
SELECT optreden.id, optreden.wedstrijd, optreden.jaartal,
liedje.titel, club.volledige_clubnaam,
SUM(score.score_lied) AS score, CASE
WHEN #prev_value = SUM(score.score_lied) THEN #rank_count
WHEN #prev_value := SUM(score.score_lied) THEN #rank_count := #rank_count + 1
END AS rank,
FROM optreden
INNER JOIN liedje ON optreden.liedje=liedje.id
INNER JOIN club ON liedje.uitvoerende_club=club.id
LEFT JOIN score ON score.optreden=optreden.id
WHERE optreden.wedstrijd="voorselectie" AND optreden.jaartal=2014
GROUP BY optreden.id
ORDER BY score_lied DESC
Please note that you might face another little problem with this kind of ranking: Normally, when two entities end up on the same rank, the next rank is not given to the next person. Here's what I mean with an example, with two persons ranking in 3:
1, 2, 3, 3, 5
But in your code, it will give:
1, 2, 3, 3, 4
I hope this helps.

Answer 2

I have tried several things. However, I had forgotten to tell you one important feature I was gonna use. The ranking of the clubs should be presented through a presentation on a big screen. Therefor the MySQL code changed a little.
I have added a support table to my database. In this support table the sum of the scores is recorded with a INSERT INTO...SELECT statement.
When this insert is done. An update script is launched which makes the ranking in the table and also makes a correct calculation for ex aequo.
Here's the update statement:
SET #rank=0, #last_score = null, #tie_build_up = 0;
UPDATE ranking_voorselectie_lied
SET rank= #rank:= if(#last_score = totaal_score_lied, #rank, #rank+#tie_build_up+1),
tie_build_up= #tie_build_up:= if(#last_score = totaal_score_lied, #tie_build_up+1, 0),
last_score= #last_score:= totaal_score_lied
WHERE wedstrijd="voorselectie" AND jaar=2014
ORDER BY totaal_score_lied DESC;
This gives me the following result:
+--------------+------+----------+-------------------+------+-----+------------+
| Wedstrijd | Jaar | Optreden | totaal_score_lied | Rank | Tie | last_score |
+--------------+------+----------+-------------------+------+-----+------------+
| voorselectie | 2014 | 12 | 792 | 1 | 0 | 792 |
| voorselectie | 2014 | 16 | 82 | 2 | 0 | 82 |
| voorselectie | 2014 | 10 | 73 | 3 | 0 | 73 |
| voorselectie | 2014 | 15 | 51 | 4 | 0 | 51 |
| voorselectie | 2014 | 3 | 50 | 5 | 0 | 50 |
| voorselectie | 2014 | 11 | 42 | 6 | 0 | 42 |
| voorselectie | 2014 | 13 | 38 | 7 | 0 | 38 |
| voorselectie | 2014 | 8 | 38 | 7 | 1 | 38 |
| voorselectie | 2014 | 14 | 37 | 9 | 0 | 37 |
| voorselectie | 2014 | 5 | 35 | 10 | 0 | 35 |
| voorselectie | 2014 | 4 | 33 | 11 | 0 | 33 |
| voorselectie | 2014 | 7 | 25 | 12 | 0 | 25 |
| voorselectie | 2014 | 9 | 23 | 13 | 0 | 23 |
+--------------+------+----------+-------------------+------+-----+------------+