我的laravel项目中有一个投票系统我每个帖子都有很多答案，每个答案都有投票，我试着显示一个有投票号码的帖子的答案。这三个表：
user_id是为了防止用户多次投票。 我试着这样做：
select p.id,a.id,count(*) from posts p, answers a, answer_votes v
where a.id=v.answer_id and p.id=a.post_id and p.id=1
group by p.id,a.id;
select a.id from answers a, posts b
where a.post_id=1
and a.id in (select v.answer_id from answer_votes v where v.vote=1 group by v.answer_id )
or a.id not in (select v.answer_id from answer_votes v where v.answer_id=a.id and v.vote=1 group by v.answer_id );
但它不起作用...请帮我解决这个问题。
答案 0 :(得分：2)
由于您没有提供任何样本数据，我创建了自己的一些：
CREATE TABLE posts (id INT, title NVARCHAR(30), content NVARCHAR(200));
CREATE TABLE answers (id INT, post_id INT, content NVARCHAR(200));
CREATE TABLE answer_votes (id INT, post_id INT, answer_id INT, user_id INT, vote bit);
示例数据：
INSERT INTO posts VALUES(1, 'Favorite Color', 'Which is your favorite color?');
INSERT INTO posts VALUES(2, 'Favorite Cheese', 'Which is your favorite cheese?');
INSERT INTO answers VALUES(1, 1, 'Black');
INSERT INTO answers VALUES(2, 1, 'Red');
INSERT INTO answers VALUES(3, 1, 'Yellow');
INSERT INTO answers VALUES(4, 1, 'Green');
INSERT INTO answers VALUES(5, 1, 'Orange');
INSERT INTO answers VALUES(6, 2, 'Parmesan');
INSERT INTO answers VALUES(7, 2, 'Mozarella');
INSERT INTO answers VALUES(8, 2, 'Swiss Cheese');
INSERT INTO answers VALUES(8, 2, 'Colby-Jac');
INSERT INTO answers VALUES(9, 2, 'Monterey Jack');
INSERT INTO answer_votes VALUES(1, 1, 1, 100, 1);
INSERT INTO answer_votes VALUES(2, 1, 2, 101, 1);
INSERT INTO answer_votes VALUES(3, 1, 3, 102, 1);
INSERT INTO answer_votes VALUES(4, 1, 4, 103, 1);
INSERT INTO answer_votes VALUES(5, 1, 5, 104, 1);
INSERT INTO answer_votes VALUES(6, 1, 5, 105, 1);
INSERT INTO answer_votes VALUES(7, 1, 5, 106, 1);
INSERT INTO answer_votes VALUES(8, 1, 3, 107, 1);
INSERT INTO answer_votes VALUES(9, 1, 3, 108, 1);
INSERT INTO answer_votes VALUES(10, 1, 2, 109, 1);
INSERT INTO answer_votes VALUES(11, 1, 2, 110, 1);
INSERT INTO answer_votes VALUES(12, 1, 2, 111, 1);
INSERT INTO answer_votes VALUES(13, 1, 5, 112, 1);
INSERT INTO answer_votes VALUES(14, 1, 5, 113, 1);
INSERT INTO answer_votes VALUES(15, 1, 5, 114, 1);
INSERT INTO answer_votes VALUES(16, 1, 1, 115, 1);
INSERT INTO answer_votes VALUES(17, 2, 6, 100, 1);
INSERT INTO answer_votes VALUES(18, 2, 7, 101, 1);
INSERT INTO answer_votes VALUES(19, 2, 7, 102, 1);
INSERT INTO answer_votes VALUES(20, 2, 7, 103, 1);
INSERT INTO answer_votes VALUES(21, 2, 7, 104, 1);
INSERT INTO answer_votes VALUES(22, 2, 6, 105, 1);
INSERT INTO answer_votes VALUES(23, 2, 6, 106, 1);
INSERT INTO answer_votes VALUES(24, 2, 8, 107, 1);
INSERT INTO answer_votes VALUES(25, 2, 8, 108, 1);
INSERT INTO answer_votes VALUES(26, 2, 9, 109, 1);
INSERT INTO answer_votes VALUES(27, 2, 9, 110, 1);
INSERT INTO answer_votes VALUES(28, 2, 7, 111, 1);
INSERT INTO answer_votes VALUES(29, 2, 7, 112, 1);
INSERT INTO answer_votes VALUES(30, 2, 6, 113, 1);
INSERT INTO answer_votes VALUES(31, 2, 7, 114, 1);
INSERT INTO answer_votes VALUES(32, 2, 8, 115, 1);
您可以使用以下查询：
SELECT posts.id,
posts.title,
posts.content as Question,
ans.content as Answer,
COUNT(votes.answer_id) as TotalVotes
FROM answers ans
INNER JOIN posts posts on ans.post_id = posts.id
INNER JOIN answer_votes votes on ans.id = votes.answer_id
WHERE votes.vote = 1
GROUP BY votes.answer_id,
posts.id,
posts.title,
posts.content,
ans.content
ORDER BY posts.id,
COUNT(votes.answer_id) DESC
您将看到以下结果集：
id title Question Answer TotalVotes
1 Favorite Color Which is your favorite color? Orange 6
1 Favorite Color Which is your favorite color? Red 4
1 Favorite Color Which is your favorite color? Yellow 3
1 Favorite Color Which is your favorite color? Black 2
1 Favorite Color Which is your favorite color? Green 1
2 Favorite Cheese Which is your favorite cheese? Mozarella 7
2 Favorite Cheese Which is your favorite cheese? Parmesan 4
2 Favorite Cheese Which is your favorite cheese? Colby-Jac 3
2 Favorite Cheese Which is your favorite cheese? Swiss Cheese 3
2 Favorite Cheese Which is your favorite cheese? Monterey Jack 2
你可以在这里看到 - ＆gt; http://sqlfiddle.com/#!9/357aef/1
注意：这不包括尚无人投票的答案。
编辑：我知道您想要包含尚无人投票的答案。您可以通过稍微修改上述查询来执行此操作：
SELECT posts.id,
posts.title,
posts.content as Question,
ans.content as Answer,
COUNT(votes.answer_id) as TotalVotes
FROM answers ans
LEFT JOIN answer_votes votes ON ans.id = votes.answer_id
LEFT JOIN posts posts ON ans.post_id = posts.id
GROUP BY posts.id,
posts.title,
posts.content,
ans.content,
votes.answer_id
ORDER BY posts.id,
COUNT(votes.answer_id) DESC
稍微修改上述数据集如下：
INSERT INTO answer_votes VALUES(1, 1, 5, 100, 1)
INSERT INTO answer_votes VALUES(16, 1, 5, 115, 1)
观察到现在没有选票“Black”的投票。此查询将产生以下结果集：
id title Question Answer TotalVotes
1 Favorite Color Which is your favorite color? Orange 8
1 Favorite Color Which is your favorite color? Red 4
1 Favorite Color Which is your favorite color? Yellow 3
1 Favorite Color Which is your favorite color? Green 1
1 Favorite Color Which is your favorite color? Black 0 /* Shows 0 votes for Black */
2 Favorite Cheese Which is your favorite cheese? Mozarella 7
2 Favorite Cheese Which is your favorite cheese? Parmesan 4
2 Favorite Cheese Which is your favorite cheese? Swiss Cheese 3
2 Favorite Cheese Which is your favorite cheese? Colby-Jac 3
2 Favorite Cheese Which is your favorite cheese? Monterey Jack 2
你可以在这里看到 - ＆gt; http://sqlfiddle.com/#!9/c4a9e5/2
希望这有帮助!!!
答案 1 :(得分：0)
SELECT p.id
, p.title
, p.content
, a.id
, a.content
, SUM(ISNULL(av.vote,0)) AS TotalVotes
FROM posts AS p
INNER
JOIN answers AS a
on p.id=a.post_id
LEFT
OUTER
JOIN answer_votes AS av
on av.answer_id=a.id
GROUP
BY p.id
, p.title
, p.content
, a.id
, a.content
ORDER
BY TotalVotes
答案 2 :(得分：0)
您需要INNER JOIN来获取相关表格的数据
尝试这样的事情：
select p.id,a.id,count(*) from posts p
INNER JOIN answers a ON p.id=a.post_id
INNER JOIN answer_votes v ON a.id=v.answer_id
where a.id=v.answer_id and p.id=a.post_id and p.id=1
group by p.id,a.id;
答案 3 :(得分：0)
这里有很多答案在SQL中。我将以PHP回答。
所以这适用于Laravel。
您需要有3个型号。运行php artisan make:model制作模型（我猜你已经知道了）。
Post.php，Answer.php，Votes.php
使用Eloquent建立关系。
在Post.php文件上，建立one-to-many关系，如下所示：
public function answers()
{
return $this->hasMany('App\Answer', 'post_id', 'id');
}
在Answer.php文件上，建立另一个one-to-many关系，如此
public function votes()
{
return $this->hasMany('App\Votes', 'answer_id', 'id');
}
现在在同一个文件上创建一个属于关系：
public function post()
{
return $this->belongsTo('App\Post', 'post_id', 'id');
}
现在您应该可以执行以下操作：
$answer = Answer::first();
$answer->post //This should get you the post the answer belongs to.
$answer->votes //Retuns all the votes an answer has. You can iterate through this array.
几乎就是这样。