比较/评估 mysql 中的两个子查询

Question

I would like to create a third select that will say pass if the score equals to maxscore, else will fail. this are the queries to evaluate...

How would I do this? Can I create a third subquery AS Status, or do I need to create on variables??

SELECT DISTINCT 
    qui.title AS Course_Name,   
    (SELECT sum(score) 
     FROM jos_jquarks_quizzes_answersessions     
     WHERE score IS NOT NULL 
       AND quizsession_id = quizSession.id     
       AND status <> -1 ) AS score, 
    (SELECT count(distinct question_id)  
     FROM jos_jquarks_quizzes_answersessions            
     WHERE quizsession_id = quizSession.id) AS maxScore,  
    (SELECT count(distinct question_id)  
     FROM jos_jquarks_quizzes_answersessions            
     WHERE quizsession_id = quizSession.id ) AS QuizStatus, 
    DATE_FORMAT(quizSession.finished_on,'%W, %M %e, %Y @ %h:%i %p') As Finished  
FROM 
    jos_jquarks_quizsession AS quizSession  
LEFT JOIN 
    jos_jquarks_users_quizzes AS users_quizzes ON users_quizzes.id = quizSession.affected_id    
LEFT JOIN 
    jos_jquarks_quizzes AS qui ON users_quizzes.quiz_id = qui.id     
LEFT JOIN 
    jos_jquarks_quizzes_answersessions AS quizSessAns ON quizSessAns.quizsession_id = quizSession.id 
LEFT JOIN 
    jos_jquarks_sessionwho AS sessionWho ON sessionWho.session_id = quizSession.id        
LEFT JOIN 
    jos_jquarks_users_profiles AS users_profiles ON users_profiles.user_id = sessionWho.user_id 
LEFT JOIN 
    jos_jquarks_profiles AS profiles ON profiles.id = users_profiles.profile_id   
WHERE 
    sessionWho.user_id = '246'

Answer 1

If you don't need to return the score or maxscore then you can simply compare the two subquery expressions:

SELECT quizSession.id, IF(
    (SELECT sum(score)
       FROM jos_jquarks_quizzes_answersessions     
       WHERE score IS NOT NULL AND quizsession_id = quizSession.id AND status <> -1) =
    (SELECT count(distinct question_id)
       FROM jos_jquarks_quizzes_answersessions
       WHERE quizsession_id = quizSession.id), "Pass", "Fail") AS status
  FROM quizSession

If you do need all of the columns, you would probably be better off writing the subqueries as joins:

SELECT quizSession.id, sum_subquery.score_sum AS score, max_subquery.max_score,
       IF(sum_subquery.score_sum = max_subquery.max_score, "Pass", "Fail") AS status
  FROM quizSession
  INNER JOIN (
    SELECT quizsession_id, sum(score) AS score_sum
      FROM jos_jquarks_quizzes_answersessions     
      WHERE score IS NOT NULL AND status <> -1
      GROUP BY quizSession_id
  ) AS sum_subquery ON quizSession.id = sum_subquery.quizsession_id
  INNER JOIN (
    SELECT quizsession_id, count(distinct question_id)
      FROM jos_jquarks_quizzes_answersessions
      GROUP BY quizsession_id
  ) AS max_subquery ON quizSession.id = max_subquery.quizsession_id

Answer 2

SELECT * from   

(SELECT sum(score) 
 FROM jos_jquarks_quizzes_answersessions     

  WHERE score IS NOT NULL AND   quizsession_id = quizSession.id     
   AND status <> -1  
UNION
 SELECT count(distinct question_id)  FROM jos_jquarks_quizzes_answersessions            
WHERE quizsession_id = quizSession.id 
UNION 

 SELECT count(distinct question_id)  FROM jos_jquarks_quizzes_answersessions            
WHERE quizsession_id = quizSession.id ) AS marksscormaxxmarkstrigger

This works well