[英]MySQL IN Condition Subquery
我有一個問題和答案列表,以及一個根據正確答案的百分比過濾問題的選項。 所以我在清單中使用以下查詢:
SELECT
question_id,
text
FROM
test_answers LEFT JOIN test_questions ON test_questions.id = test_answers.question_id
LEFT JOIN test_categories ON test_questions.`category_id` = test_categories.id
WHERE `question_id` IN(question IDS)
GROUP BY `question_id`
ORDER BY `question_id` DESC;
並使用另一個查詢來查找問題IDS,其正確答案的百分比在給定范圍內。 查詢如下:
SELECT q1.question_id FROM (
SELECT test_answers.question_id AS question_id,
SUM( IF( test_answers.correct_answer =1, 1, 0 ) ) AS correct_answers,
SUM( IF( test_answers.correct_answer !=1, 1, 0 ) ) AS incorrect_answers,
round( ( SUM( IF( test_answers.correct_answer =1, 1, 0 ) ) / ( SUM( IF( test_answers.correct_answer =1, 1, 0 ) ) + SUM( IF( test_answers.correct_answer !=1, 1, 0 ) ) ) *100 ) , 2 ) AS percentage
FROM test_replies
JOIN test_answers ON test_replies.answer_id = test_answers.id
GROUP BY test_answers.question_id
HAVING percentage between 80 and 89 AND correct_answers >25
) AS q1
現在的問題是,第二個查詢將返回近4000個問題ID,並且在不久的將來會增加,並且可能會變成10k或更多。 因此,我非常想優化查詢,因為它將極大地影響性能。 有人可以建議一種更好的方法嗎?
嘗試加入而不是IN
,看看是否有幫助。 (未測試sql)
SELECT
ta.question_id, text
FROM
(
SELECT test_answers.question_id AS question_id,
SUM( IF( test_answers.correct_answer =1, 1, 0 ) ) AS correct_answers,
SUM( IF( test_answers.correct_answer !=1, 1, 0 ) ) AS incorrect_answers,
round( ( SUM( IF( test_answers.correct_answer =1, 1, 0 ) ) / ( SUM( IF( test_answers.correct_answer =1, 1, 0 ) ) + SUM( IF( test_answers.correct_answer !=1, 1, 0 ) ) ) *100 ) , 2 ) AS percentage
FROM test_replies
JOIN test_answers ON test_replies.answer_id = test_answers.id
GROUP BY test_answers.question_id
HAVING percentage between 80 and 89 AND correct_answers >25
) AS q1
INNER JOIN
test_answers ta USING (question_id)
LEFT JOIN
test_questions ON test_questions.id = ta.question_id
LEFT JOIN
test_categories ON test_questions.`category_id` = test_categories.id
GROUP BY
ta.question_id`
ORDER BY
ta.question_id DESC;
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