Question

我在php和mysql中创建了一个投票系统。当用户对id进行投票时，在引用FK media_id的“投票”中插入记录。当我显示条目时，我使用此查询来获取每个条目的投票数：

$sql = "SELECT COUNT(*) FROM insta_votes WHERE media_id ='".$mediaid."'";
if ($res = $db->query($sql)) {
    return $res->fetchColumn();
}
return 0;

这很好，但我希望能够按照他们的投票数对结果进行排序。最好只使用一个查询。我怎样才能做到这一点？

表的结构如下：

votes table
+-----------+--------------+------+-----+-------------------+----------------+
| Field     | Type         | Null | Key | Default           | Extra          |
+-----------+--------------+------+-----+-------------------+----------------+
| id        | int(11)      | NO   | PRI | NULL              | auto_increment |
| media_id  | varchar(255) | NO   |     | NULL              |                |
| ip        | varchar(20)  | NO   |     | NULL              |                |
| c_time    | timestamp    | NO   |     | CURRENT_TIMESTAMP |                |
| sessionid | varchar(30)  | NO   |     | NULL              |                |
+-----------+--------------+------+-----+-------------------+----------------+

entries table
+---------------+--------------+------+-----+-------------------+-------+
| Field         | Type         | Null | Key | Default           | Extra |
+---------------+--------------+------+-----+-------------------+-------+
| page_id       | int(11)      | NO   | MUL | NULL              |       |
| media_id      | varchar(255) | NO   | PRI | NULL              |       |
| url           | varchar(255) | NO   |     | NULL              |       |
| c_time        | datetime     | NO   |     | NULL              |       |
| likes         | int(11)      | YES  |     | NULL              |       |
| deleted       | tinyint(1)   | NO   |     | 0                 |       |
| inserted_time | timestamp    | YES  |     | CURRENT_TIMESTAMP |       |
| numReports    | int(11)      | NO   |     | 0                 |       |
+---------------+--------------+------+-----+-------------------+-------+

谢谢！

Answer 1

如果我正确理解了表格（我可能没有），则每个entries行可能会引用多个votes行。在这种情况下，您需要的查询将是这样的：

SELECT
  entries.page_id,
  COUNT(*) AS VoteCount
FROM entries
INNER JOIN votes ON entries.media_id = votes.media_id
GROUP BY entries.page_id
ORDER BY VoteCount

如果您在entries列表中添加其他SELECT列，请务必将其添加到GROUP BY列表中。

附录：@JuanPabloCalifano正确地指出，此查询不包含零投票的条目。以下是如何包含它们：

SELECT
  entries.page_id,
  COALESCE(COUNT(votes.id), 0) AS VoteCount
FROM entries
LEFT JOIN votes ON entries.media_id = votes.media_id
GROUP BY entries.page_id
ORDER BY VoteCount

Answer 2

SELECT COUNT(*) as CNT, `media_id` FROM `insta_votes` GROUP BY `media_id` order by 1;

Answer 3

SELECT COUNT(*), media_id FROM insta_votes 
GROUP BY media_id 
ORDER BY COUNT(*);"

Mysql一对多的关系。按第二个表中的行数排序

3 个答案: