php - 获取同一id的最高分，然后与其他id比较

Question

桌子 ：

========================================
|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 |
========================================

我想在每个中获得最高分，document_id然后将结果与其他结果进行比较document_id。我的目标是获得序列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'];
}

我仍然得到错误的结果。请帮我。

Answer 1

您似乎描述的 SQL 是：

SELECT document_id
        , MAX(score) as max_score
    FROM tb_score
    GROUP BY document_id
    ORDER BY MAX(score) DESC --or max_score, I'm not sure which MySQL will accept.

这有帮助吗？

另外： MySQL扩展在 PHP 中已弃用，您应该使用MySQL 改进或PHP 数据对象来完成这项工作。

Answer 2

您不能 在ORDER BY. 所以你必须使用MAX(score)in ORDER BY。像这样：

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

或者使用子查询你可以做同样的事情。

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

看到这个 SQLFiddle

Answer 3

SQL必须是这样的。

SELECT document_id, MAX(score) as max_score 
FROM `tb_score` GROUP BY document_id
ORDER BY max_score DESC