smallkun/class-notes
smallkun/class-notes
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Auto commit

Browse Source
This commit is contained in:
smallkun 2025-02-25 09:51:43 +08:00
parent 10a4acf101
commit d44aeed220
1 changed files with 25 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
2207/MySQL练习题/查询练习.md
View File

@ -332,9 +332,33 @@ FROM scores sc, students st
WHERE sc.course_id = '01' AND sc.score < 60 AND sc.student_id = st.id
ORDER BY sc.score DESC;
#13.按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩
#13.按平均成绩从高到低显示所有学生的所有课程的平均成绩
SELECT c.`name`, AVG(sc.score)
FROM scores sc, courses c
WHERE sc.course_id = c.id
GROUP BY c.id
ORDER BY AVG(sc.score) DESC;
#14.查询各科成绩最高分、最低分和平均分：以如下形式显示：课程 ID，课程 name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率；（及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90）
SELECT c.id '课程ID', c.`name` '课程名称', MAX(s.score) '最高分', MIN(s.score) '最低分', ROUND(AVG(s.score), 1) '平均值'
FROM scores s, courses c
WHERE s.course_id = c.id
GROUP BY c.id;
SELECT s.course_id,
CONCAT(TRUNCATE(COUNT(IF(s.score >=60, TRUE, NULL))/sc.count*100,2), '%') s1,
CONCAT(TRUNCATE(COUNT(IF(s.score >=70 AND s.score < 80, TRUE, NULL))/sc.count*100,2), '%') s2,
CONCAT(TRUNCATE(COUNT(IF(s.score >=80 AND s.score < 90, TRUE, NULL))/sc.count*100,2), '%') s3,
CONCAT(TRUNCATE(COUNT(IF(s.score >=90, TRUE, NULL))/sc.count*100,2), '%') s4
FROM scores s, (
SELECT course_id, COUNT(*) count
FROM scores
GROUP BY course_id
) sc
WHERE s.course_id = sc.course_id
GROUP BY s.course_id;
#15.按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺