Question

有没有办法优化以下查询？

SELECT s1.* FROM
(SELECT s.* 
FROM answer a, answer_item ai, sessions s
WHERE s.session_state='FINISHED' AND a.sessionId=s.id AND ai.answer=a.id
AND a.question=1001 AND ai.question_variant_id=1103) s1, 
(SELECT s.* 
FROM answer a, answer_item ai, sessions s
WHERE s.session_state='FINISHED' AND a.sessionId=s.id AND ai.answer=a.id
AND a.question=1003 AND ai.question_variant_id=1301) s2
WHERE s1.id=s2.id

除了这些部分外，一切似乎都是一样的：

a.question=1001 AND ai.question_variant_id=1103
a.question=1003 AND ai.question_variant_id=1301

Answer 1

SELECT s.* 
FROM answer a
JOIN answer_item ai ON ai.answer=a.id
JOIN sessions s ON a.sessionId=s.id
WHERE s.session_state='FINISHED'
AND 
(
      a.question=1001 AND ai.question_variant_id=1103
   OR a.question=1003 AND ai.question_variant_id=1301
)

Answer 2

检查以下优化查询。

SELECT  s.* FROM  FROM answer a, answer_item ai, sessions s
WHERE s.session_state='FINISHED' AND a.sessionId=s.id AND ai.answer=a.id
AND ( 
   (a.question=1001 AND ai.question_variant_id=1103)
   OR 
   (a.question=1003 AND ai.question_variant_id=1301)
)

Answer 3

尝试这一次（JOIN表answer和answer_item两次）：

SELECT s.* 
FROM answer a
JOIN answer_item ai ON ai.answer=a.id
JOIN sessions s ON a.sessionId=s.id
JOIN answer a2 ON s.id=a2.sessionId
JOIN answer_item ai2 ON ai2.answer=a2.id
WHERE s.session_state='FINISHED'
AND ( (a.question=1001 AND ai.question_variant_id=1103)
AND (a2.question=1003 AND ai2.question_variant_id=1301) )

Answer 4

这似乎是在寻找回答这两个问题的会议（或其他）。我认为以下内容可能会为您提供所需的行。但是，您可能需要做更多工作才能获得正确的列：

  SELECT s.* 
  FROM answer a JOIN
       answer_item ai
       ON ai.answer = a.id JOIN
       sessions s
       ON a.sessionId = s.id
  WHERE s.session_state = 'FINISHED' AND
        (a.question = 1001 AND ai.question_variant_id = 1103 OR
         a.question = 1003 AND ai.question_variant_id = 1101
        )
  GROUP BY s.id
  HAVING SUM(a.question = 1001 AND ai.question_variant_id = 1103) > 0 AND
         SUM(a.question = 1003 AND ai.question_variant_id = 1101) > 0

使用几乎相同的子查询优化mySQL查询

4 个答案: