Question

我有这样的表设置：

用户表：

ID | Username | Password
1  |   Humza  |   123
3  |   God    |   145

问题表：

Question_ID| Question_Title   | Question      | Rating | Category ID | User ID |
    1      | Testing Display  | Did it Work   |  55    |      2      |    3    |
    2      | Foo is love?     | Same as Above | -100   |      2      |    1    |
    3      | Bla              | Baa Black XD  | 909    |      2      |    1    |

答案表：

Answer_ID| Answer   | Answer_Rating     | Answer_User_ID    | Question_ID |
 1       | YES      |       909         |     1             |      2      | 
 2       | Wohoo    |        15         |     3             |      2      |

声望表：

Reputation_ID| Reputation | User_Rep_ID|
 1           |   -50      |     1      |
 2           |   9999     |     3      |

类别表：

Category_ID  |    Category      | 
 1           |   Dr Who         |    
 2           |  Programming     |  
 3           |   Music          |

我的现有查询从第2类中挑选问题：

SELECT u.username, r.Reputation, q.Question_Title,
q.Question, q.Rating, c.Category, count(a.Answer_ID) as num_answers

FROM Questions q 
INNER JOIN Users u ON u.id = q.User_ID
INNER JOIN Reputation r on r.User_Rep_ID = u.id
INNER JOIN Categorys c ON c.Category_ID = q.Category_ID
LEFT OUTER JOIN Answers a on q.Question_ID = a.Question_ID
WHERE q.Category_ID = 2
GROUP BY a.Question_ID

然而由于某种原因，这不能解决第三个问题，所以它并不完美。

当前查询挑选答案：

SELECT u.username as AnswerUserName,
a.Answer, a.Answer_Rating, r.Reputation as AnswerReputation

FROM Answers a
INNER JOIN Users u ON u.ID = a.Answer_User_ID
INNER JOIN Questions q on q.Question_ID = a.Question_ID
LEFT OUTER JOIN Reputation r ON r.User_Rep_ID = u.ID

WHERE a.Question_ID = q.Question_ID

然而，无论问题是否有答案，这似乎只是挑出两个答案。因此，当我查询类别1中的所有问题时，将显示相同的答案，并且我不确定原因。

现在我会尽力解释：

1）我需要3个单独的查询，它会在第1,2和3类中选择所有问题以及发布它们的用户及其声誉。除此之外，它还必须计算每个类别中每个问题的答案数。 修改 - 完成

2）我需要第二个查询，它将获得每个类别中有答案的问题的所有答案，回答问题的人的用户名及其声誉。

我将如何实现这一目标？如果您需要更多详细信息，请随时提出。

Answer 1

实际上，我不确定为什么这会起作用。初始查询中的非聚合字段不在GROUP BY语句中。此外，既然你知道不是每个问题都会得到答案，我就不会用A.Question_ID分组 - 而是用q.question_Id分组。试试这个：

SELECT u.username, r.Reputation, q.Question_Title,
q.Question, q.Rating, c.Category, count(a.Answer_ID) as num_answers
FROM Questions q 
INNER JOIN Users u ON u.id = q.User_ID
INNER JOIN Reputation r on r.User_Rep_ID = u.id
INNER JOIN Categorys c ON c.Category_ID = q.Category_ID
LEFT OUTER JOIN Answers a on q.Question_ID = a.Question_ID
WHERE q.Category_ID = 2
GROUP BY u.username, r.Reputation, q.Question_Title,
q.Question, q.Rating, c.Category

基于其他查询形成查询？

1 个答案: