带计数的简单sql查询

我正在使用SQLite。 我需要一个简单问题的帮助。 这是我的三张桌子：

--------------
problem
--------------
id (primary key)
question_id (foreign key)

--------------
question
--------------
id (primary key)
answer_id (foreign key)

--------------
answer
--------------
id (primary key)

我想得到在一个问题的每个问题中至少有N个答案的所有问题。我给你举个例子：

-------
problem
id 
1
2


-------
question 
id   problem_id
1    1
2    1
3    1
4    2

-------
answer
id   question_id
1    1
2    1
3    1
4    2
5    2
6    3
7    4
8    4

如果n=2，我的结果应该是problem_id=2

我试过这个：

   select distinct question.problem_id 
   from answer, question
   where answer.question_id = question.id
   group by answer.question_id
   having count(*) >= 2

但它不起作用，因为它至少有一个问题有两个答案。所有问题都必须满足该条件

有什么问题吗

select problem_id
from
(
    select q.problem_id, q.id, count(a.id) answercount
    from question q
    left join answer a on a.question_id = q.id
    group by q.problem_id, q.id
) g
group by problem_id
having min(answercount) >= 2

备选示例4答案

---

以下是我对T-SQL中的问题的看法：

declare @problem table(id bigint not null primary key clustered)
declare @question table(id bigint not null primary key clustered, problem_id bigint)
declare @answer table(id bigint not null primary key clustered, question_id bigint)

declare @n int = 2

insert @problem
      select 1 
union select 2

insert @question
      select 1, 1 
union select 2, 1
union select 3, 1
union select 4, 2

insert @answer 
      select 1, 1 
union select 2, 1
union select 3, 1
union select 4, 2
union select 5, 2
union select 6, 3
union select 7, 4
union select 8, 4

select p.id --, p.name, p.description, p.etc
from @problem p
where @n >= ALL --http://msdn.microsoft.com/en-us/library/ms178543.aspx
(
    select COUNT(a.id) 
    from @question q
    left outer join @answer a
        on q.id = a.question_id
    where p.id = q.problem_id
    group by q.id
)

注意：表模式与问题略有不同，因为问题中的模式与示例数据不匹配

另类

基于@RichardTheKiwi的答案，将内部SQL移到临时表中

declare @tempTable table (pid bigint, qid bigint, aidCount bigint)

insert @tempTable
select q.problem_id, q.id, count(a.id) answercount
from @question q
left join @answer a on a.question_id = q.id
group by q.problem_id, q.id

select pid
from @tempTable
group by pid 
having min(aidCount) >= @n 

---

作为相关子查询重写。我们不是在每个问题中找到至少有N个答案的问题，而是找到没有问题的答案少于N个的问题：

SELECT id AS problem_id
FROM problem AS p 
WHERE NOT EXISTS
      ( SELECT 1
        FROM question AS q
          LEFT JOIN answer AS a 
            ON a.question_id = q.id
        WHERE q.problem_id = p.id
        GROUP BY q.id
        HAVING COUNT(a.question_id) < 2
      ) ;

---

这似乎是正确的，但我的sqlite版本有一些问题，所以在执行select from select时出现了一个错误。。。。是否有其他方法编写该查询？谢谢我没有忘记。在外部软件中，它可能使用不同的sqlite版本，但在我的软件中，它不工作，我无法更改它，因此我必须以另一种方式编写该查询，可能使用INTERSECT？我为您添加了一个替代查询库。您能解释一下替代查询中的条件minanswercount>=2在哪里吗？结果与第一个不同。也许这就是我错过了不同结果的地方。它可以左键连接两次以得到两个不同的答案a.iddeclare @tempTable table (pid bigint, qid bigint, aidCount bigint) insert @tempTable select q.problem_id, q.id, count(a.id) answercount from @question q left join @answer a on a.question_id = q.id group by q.problem_id, q.id select pid from @tempTable group by pid having min(aidCount) >= @n

SELECT id AS problem_id
FROM problem AS p 
WHERE NOT EXISTS
      ( SELECT 1
        FROM question AS q
          LEFT JOIN answer AS a 
            ON a.question_id = q.id
        WHERE q.problem_id = p.id
        GROUP BY q.id
        HAVING COUNT(a.question_id) < 2
      ) ;