mysql计数结果状态正确并按用户ID分组

Question

I made a query in which there are result being compared from a pre defined answers table to the answers which a user enters for multiple questions . The problem is now i want to get the total score (which i can calculate according to status correct ) of each user . The following query gives me all the users data with status of each question's answer to be correct or not .

SELECT qa.question_id, qa.test_id, uta.user_answer,uta.user_id,  qa.type,
qa.answers correct_answer,
CASE WHEN uta.user_answer = qa.answers THEN 'correct' ELSE 'incorrect' END
AS status
FROM questions_answer qa
LEFT JOIN 
(
  SELECT user_id, type, test_id, question_id,
  GROUP_CONCAT(answers ORDER BY answers) AS user_answer,
  timestamp from user_test_answers
  WHERE  test_id = '1'    
  GROUP BY user_id, question_id

) uta
ON qa.question_id = uta.question_id 
where qa.test_id=1 

If i add GROUP BY user_id in the end it also groups the result by user_id But how to count all the status correct so that i can get the total number of correct answers count .

Answer 1

First of all, you're misusing, and proposing to misuse, GROUP BY . When you use it correctly, every column in your result set is either also mentioned in the GROUP BY clause or is an aggregate column. Please read up on GROUP BY and use it correctly or you'll have a hard time troubleshooting your queries.

Secondly, you can wrap your query up in an outer aggregate query and do the summary. This kind of thing should work, as long as the query in your question works.

SELECT user_id, test_id, 
       100 * SUM(status='correct')   / COUNT(status) AS percent_correct, 
       100 * SUM(status='incorrect') / COUNT(status) AS percent_incorrect
  FROM (
          /* your entire query from your question */
       ) AS results
 GROUP BY user_id, test_id
 ORDER BY user_id, test_id