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smallkun 2025-02-25 19:58:01 +08:00
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2207/MySQL练习题/查询练习.md
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@ -366,11 +366,45 @@ GROUP BY c.id;
#16.查询学生的总成绩，并进行排名，总分重复时保留名次空缺 #16.查询学生的总成绩，并进行排名，总分重复时保留名次空缺
#16.1查询学生的总成绩，并进行排名，总分重复时不保留名次空缺
#16.1查询学生的总成绩，并进行排名，总分重复时不保留名次空缺
SELECT sc.`name`, sc.s, @rank:=@rank+1
FROM (
SELECT st.`name`, IFNULL(SUM(sc.score),0) s
FROM students st
LEFT JOIN scores sc ON st.id = sc.student_id
GROUP BY st.id
ORDER BY s DESC
)sc, (SELECT @rank:=0) r;
#17.统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比 #17.统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比
#18.查询各科成绩前三名的记录 #18.查询各科成绩前三名的记录
SELECT s1.sname, s1.cname, s1.score, s1.rank1
FROM (
SELECT st.`name` sname, c.`name` cname, sc.score, @rank1:=@rank1+1 rank1
FROM students st, scores sc, courses c, (SELECT @rank1:=0) r
WHERE st.id = sc.student_id AND c.id = sc.course_id AND course_id = '01'
ORDER BY sc.score DESC
LIMIT 3
)s1
UNION
SELECT s2.sname, s2.cname, s2.score, s2.rank1
FROM (
SELECT st.`name` sname, c.`name` cname, sc.score, @rank2:=@rank2+1 rank1
FROM students st, scores sc, courses c, (SELECT @rank2:=0) r
WHERE st.id = sc.student_id AND c.id = sc.course_id AND course_id = '02'
ORDER BY sc.score DESC
LIMIT 3
)s2
UNION
SELECT s3.sname, s3.cname, s3.score, s3.rank1
FROM (
SELECT st.`name` sname, c.`name` cname, sc.score, @rank3:=@rank3+1 rank1
FROM students st, scores sc, courses c, (SELECT @rank3:=0) r
WHERE st.id = sc.student_id AND c.id = sc.course_id AND course_id = '03'
ORDER BY sc.score DESC
LIMIT 3
)s3;
#19.查询每门课程被选修的学生数 #19.查询每门课程被选修的学生数