Question

我试图想出一个SQL查询来计算前五个用户，这些用户的答案成功率最高。我有一个查询可以检索回答最多问题的前五位用户，如果答案是正确的，则无关紧要

SELECT b.user_id, 
   Count(1) AS answers, 
   username
FROM   score a 
   JOIN processedquestion b 
     ON a.attempt_id = b.attempt_id 
   JOIN users c 
     ON b.user_id = c.user_id 
WHERE  selected_answer IS NOT NULL 
GROUP  BY user_id 
ORDER  BY Count(1) DESC 
LIMIT  5

我的查询前五位用户的答案最正确

SELECT b.user_id, 
   Count(1) AS correct_answers, 
   username 
FROM   score a 
   JOIN processedquestion b 
     ON a.attempt_id = b.attempt_id 
   JOIN users c 
     ON b.user_id = c.user_id 
WHERE  selected_answer = correct_answer 
GROUP  BY user_id 
ORDER  BY Count(1) DESC 
LIMIT  5

我要做的是查询现在将按其所有答案的成功率百分比返回前五名用户。因此，如果用户只回答了一个问题并且它是正确的，那么它们将在查询中以100％的成功率返回。我正在使用的表是

ProcessedQuestions(attempt_id, user_id, question_id, attempt_datetime)
Score(score_id, attempt_id, correct_answer, selected_answer)
Users(user_id, first_name, last_name)

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Answer 1

您可以使用条件聚合。在MySQL中，使用avg()：

非常简单

SELECT b.user_id, username, count(*) as answers,
       avg(selected_answer = correct_answer) as p_correct
FROM score a JOIN
     processedquestion b 
     ON a.attempt_id = b.attempt_id JOIN
     users c 
     ON b.user_id = c.user_id 
WHERE selected_answer IS NOT NULL 
GROUP BY user_id 
ORDER BY p_correct DESC
LIMIT 5;

SQL查询用于计算回答问题成功率最高的用户

1 个答案: