Question

您好我想写一个mysql查询，它提供了条件明智的结果。

例如，

。我有一个表格，包含问题，答案值，用户选择的值字段。

用户可以多次参加回答该问题。

qid     rightanz     wronganz
11         4             2
11         4             4
11         4             1
25         1             1

I want out put like this
qid     rightanz     wronganz
11          1            2   
25          1            0

我想显示用户为该问题提供正确和错误答案的次数？我怎么能写一个mysql查询呢？任何人都可以帮助我吗？

Answer 1

SELECT SUM(IF(answer = 42, 1, 0)) AS correct_count, count(*) as total_count
FROM answers
WHERE user_id = 13

假设您要检查的user_id为13，正确答案为42

Answer 2

对于所有问题

SELECT a.userId, q.qid
,SUM( CASE WHEN q.answer = a.answer THEN 1 ELSE 0 END) AS correct_answers
,SUM( CASE WHEN q.answer = a.answer THEN 0 ELSE 1 END) AS wrong_answers
FROM questions q
JOIN answers a ON q.qid = a.qid
GROUP BY a.userId, q.qid

针对具体问题

SELECT a.userId
,SUM( CASE WHEN q.answer = a.answer THEN 1 ELSE 0 END) AS correct_answers
,SUM( CASE WHEN q.answer = a.answer THEN 0 ELSE 1 END) AS wrong_answers
FROM questions q
JOIN answers a ON q.qid = a.qid
WHERE q.qid = <question_id>
GROUP BY a.userId

如何编写条件明智的结果提供查询？

2 个答案: