Question

table :

========================================
|id| document_id | sentence_id | score |
========================================
|1 |   3         |     1       | 0.324 |
|2 |   3         |     2       | 0.201 |
|3 |   5         |     1       | 0.181 |
|4 |   5         |     2       | 0.402 |
========================================

I wanna get maximum score in every document_id and then compare the result with other document_id. My goal is to get the sequence of document_id. so from the example, the result must be 5 3

$q = mysql_query("SELECT document_id, MAX(score) as max_score FROM `tb_score` GROUP BY document_id ");
while ($row = mysql_fetch_array($q)) {
   $min = $row['max_score'];
}

I still get a wrong result. Please, help me.

Answer 1

You can’t use alias in ORDER BY. So you have to use MAX(score) in ORDER BY. Like this:

SELECT document_id ,MAX(score) as Highscore
FROM tb_score
GROUP BY document_id
ORDER BY MAX(score) DESC;

OR using sub-query you can do the same.

SELECT * FROM
(
SELECT document_id ,MAX(score) as Highscore
FROM tb_score
GROUP BY document_id
) A
ORDER BY Highscore DESC;

See this SQLFiddle