[英]SQL Query Optimization - eliminate subquery
我有這個查詢,我想優化它。 我使用SELECT和子查詢,如果可能的話我只想使用一個SELECT。
有沒有人對它有任何想法?
先感謝您
SELECT c.*
FROM course AS c
JOIN student_course AS sc ON c.id = uc.course_id
WHERE sc.student_id = '5' AND c.level = (SELECT MAX(level)
FROM course
JOIN student_course ON c.id = sc.course_id)
GROUP BY c.category_id
SELECT c.*
FROM course AS c
JOIN student_course AS sc
ON c.id = sc.course_id
WHERE sc.student_id = '5'
GROUP BY c.category_id
having c.level = MAX(sc.level)
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