sql - SQL查询优化——消除子查询

Question

我有这个查询，我想优化它。我使用一个 SELECT 和一个子查询，如果可能的话，我只想使用一个 SELECT。

有人对此有任何想法吗？

先感谢您

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 

Answer 1

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)