Php 如何按计数或其他表中的某些条件排序

我有一个创建问答网站的项目。
我想通过这些条件显示问题。

1.通过最新的问题显示，是的，我只知道order by

created desc

2.按大多数答案显示和排序问题。
3.按投票最多的人对问题进行显示和排序。（和大多数答案一样）。
4.在未回答的地方显示问题

这是我在数据库中的表结构。

TABLE question
COLUMNS
q_id (primary key)
userid
title
content
created

TABLE answer
COLUMNS
a_id (primary key)
userid
q_id
content
created

TABLE vote
COLUMNS
userid
q_id
created

每个表可以有一百万行

对于我上面的4个问题，我正在尝试这些

SQL

。

1显示最新问题。（已解决）

select * from question order by created desc

SELECT q.*, COUNT(a.id) as answerCount
FROM question q
LEFT JOIN answer a
        ON (q.q_id = a.q_id)
ORDER BY answerCount DESC

SELECT q.*, COUNT(v.id) as voteCount
FROM question q
LEFT JOIN vote v
        ON (q.q_id = v.q_id)
ORDER BY voteCount DESC

SELECT q.* 
    FROM question q
    LEFT JOIN answer a 
        ON p.q_id = a.q_id
    WHERE a.q_id IS NULL ORDER BY q.created DESC

2按大多数答案显示和排序。（似乎慢了）

select * from question order by created desc

SELECT q.*, COUNT(a.id) as answerCount
FROM question q
LEFT JOIN answer a
        ON (q.q_id = a.q_id)
ORDER BY answerCount DESC

SELECT q.*, COUNT(v.id) as voteCount
FROM question q
LEFT JOIN vote v
        ON (q.q_id = v.q_id)
ORDER BY voteCount DESC

SELECT q.* 
    FROM question q
    LEFT JOIN answer a 
        ON p.q_id = a.q_id
    WHERE a.q_id IS NULL ORDER BY q.created DESC

3按多数投票人显示和排序。（似乎慢了）。

select * from question order by created desc

SELECT q.*, COUNT(a.id) as answerCount
FROM question q
LEFT JOIN answer a
        ON (q.q_id = a.q_id)
ORDER BY answerCount DESC

SELECT q.*, COUNT(v.id) as voteCount
FROM question q
LEFT JOIN vote v
        ON (q.q_id = v.q_id)
ORDER BY voteCount DESC

SELECT q.* 
    FROM question q
    LEFT JOIN answer a 
        ON p.q_id = a.q_id
    WHERE a.q_id IS NULL ORDER BY q.created DESC

4显示未回答的问题。（似乎慢了）

select * from question order by created desc

SELECT q.*, COUNT(a.id) as answerCount
FROM question q
LEFT JOIN answer a
        ON (q.q_id = a.q_id)
ORDER BY answerCount DESC

SELECT q.*, COUNT(v.id) as voteCount
FROM question q
LEFT JOIN vote v
        ON (q.q_id = v.q_id)
ORDER BY voteCount DESC

SELECT q.* 
    FROM question q
    LEFT JOIN answer a 
        ON p.q_id = a.q_id
    WHERE a.q_id IS NULL ORDER BY q.created DESC

注意：如果使用

内部联接

则不会选择count=0的行。

TABLE question
COLUMNS
q_id (primary key)
userid
title
content
created

TABLE answer
COLUMNS
a_id (primary key)
userid
q_id
content
created

TABLE vote
COLUMNS
userid
q_id
created

正如我所想，其他网站通常都有字段来计算

答案

和

投票

？为了加快速度，我应该改成这个还是他们有一些算法，不需要在

问题
表中计算答案和投票

TABLE question
COLUMNS
q_id (primary key)
userid
title
content
created
answer_count
votes_count

非常感谢您的帮助或建议。
您可以尝试重新编写您的查询，但由于MySQL更喜欢连接而不是更直接的方式，因此它们不太可能更快。以下是一些您可以尝试的查询：

按大多数答案显示和排序。使用GROUP BY和COUNT（*）明确说明您的工作。

SELECT q.*, COUNT(*) as answerCount
FROM question q
LEFT JOIN answer a ON a.q_id = q.q_id
GROUP BY q.q_id
ORDER BY answerCount DESC;

SELECT q.*, (select count(*) from answers a where a.q_id = q.q_id) as answerCount
FROM question q
ORDER BY answerCount DESC;

SELECT q.*, a.answerCount
FROM question q
LEFT JOIN (select q_id, count(*) as answerCount from answers group by q_id) a
  ON a.q_id = q.q_id
ORDER BY a.answerCount DESC;

按大多数答案显示和排序。在子查询中计数。

SELECT q.*, COUNT(*) as answerCount
FROM question q
LEFT JOIN answer a ON a.q_id = q.q_id
GROUP BY q.q_id
ORDER BY answerCount DESC;

SELECT q.*, (select count(*) from answers a where a.q_id = q.q_id) as answerCount
FROM question q
ORDER BY answerCount DESC;

SELECT q.*, a.answerCount
FROM question q
LEFT JOIN (select q_id, count(*) as answerCount from answers group by q_id) a
  ON a.q_id = q.q_id
ORDER BY a.answerCount DESC;

按大多数答案显示和排序。派生表查询中的计数。

SELECT q.*, COUNT(*) as answerCount
FROM question q
LEFT JOIN answer a ON a.q_id = q.q_id
GROUP BY q.q_id
ORDER BY answerCount DESC;

SELECT q.*, (select count(*) from answers a where a.q_id = q.q_id) as answerCount
FROM question q
ORDER BY answerCount DESC;

SELECT q.*, a.answerCount
FROM question q
LEFT JOIN (select q_id, count(*) as answerCount from answers group by q_id) a
  ON a.q_id = q.q_id
ORDER BY a.answerCount DESC;

在未回答的地方显示问题。也就是说，如果没有答案：

SELECT q.*
FROM question q
WHERE NOT EXISTS (select * from answer a where a.q_id = q.q_id)
ORDER BY q.created DESC;

但是，如前所述，这些更直接的查询不一定更快。不管怎样，你都可以试一下

因此，如果重新编写查询没有加快速度，那么，是的，您可以将答案和计票添加到您的问题表中。这当然是多余的，但如果需求需要这样做，那么就采取行动
 您可以使用左连接来选择count=0的行，并加快添加索引或转到存储过程的过程