Question

我有4张桌子

Users
ID
Name

Questions
ID
Question


User_Answers
ID
User_ID
Answer
Question_ID


Correct_Answers
ID
Question_ID
Answer_ID

所以例如，我有这些数据

Users
ID = 3
Name = Jack
ID = 4
Name = Mike
--------------------
Questions

ID = 3
Question = text for a question
ID = 4
Question = text for a question
-----------------

User_Answers
ID = 1
User_ID = 3
Answer = 0
Question_ID = 3

ID = 2
User_ID = 3
Answer = 1
Question_ID = 3

ID = 3
User_ID = 3
Answer = 1
Question_ID = 3

ID = 4
User_ID = 3
Answer = -1
Question_ID = 3

ID = 5
User_ID = 3
Answer = 0
Question_ID = 3

ID = 6
User_ID = 3
Answer = 1
Question_ID = 3

-------------------------

Correct_Answers
ID = 1
Question_ID  = 3
Answer = 0

ID = 2
Question_ID  = 4
Answer = -1

ID = 3
Question_ID  = 5
Answer = 0

我需要sql查询才能让我获得最正确答案的用户

SELECT * 
FROM users,correct_answers,questions,user_answers 
WHERE correct_answers.answer = user_answers.answer 
  AND user_answers.question_id = correct_answers.question_id

这不会像我想的那样工作，我需要一个子查询来计算正确答案并得到最大值:(

这是sqlfiddle链接

http://sqlfiddle.com/#!2/b53a7/3

我怎么能这样做？

由于

Answer 1

Select a.user_id, count(b.ID) as maxAnswers 
from user_answers a 
inner join correct_answers b on a.answer=b.answer 
and a.question_id = b. question_id 
group by a.user_id 
order by maxAnswers desc 
limit 1;

Answer 2

对于具有最正确答案的用户的表结构查询：

Select sq.User_ID, sq.Name, sum(Correctness) as Most_Correct
  from (select ua.User_ID, u.Name, if(ua.Answer = ca.Answer, 1, 0) as 
    Correctness from  Users_Answers ua join Questions q 
      on ua.Question_ID = q.ID join correct_answers ca
       on ua.Question_ID= ca.Question_ID join Users u on ua.User_ID = u.ID) as sq
  group by User_ID Desc Order by Most_Correct desc limit 1;

http://sqlfiddle.com/#!2/6aa82/1

您还可以按如下方式创建架构：

用户

ID    |      Name

问题

ID    |      Question     |    Answer

User_Answers

ID    |      User_ID      |    Answer      |    Question_ID

查询具有最正确答案的用户：

Select sq.User_ID, sq.Name, sum(Correctness) as Most_Correct
   from (select ua.User_ID, u.Name, if(ua.Answer = q.Answer, 1, 0) as Correctness
      from  User_Answers ua join Questions q 
          on ua.Question_ID = q.ID join User u on ua.User_ID = u.ID) as sq
              group by User_ID Desc Order by Most_Correct desc limit 1;

在3个表中为用户选择最大正确答案

2 个答案: