tb_student(sid,sname,sage,ssex) 学生表
sid：学号；sname：学生姓名；sage：学生年龄；ssex：学生性别
tb_course(cid,cname,tid) 课程表
cid,课程编号；cname：课程名字；tid：教师编号
tb_sc(sid,cid,score) 成绩表
sid：学号；cid,课程编号；score：成绩
tb_teacher(tid,tname) 教师表
tid：教师编号； tname：教师名字
tb_student：学生表 |
|
sid |
学号 |
sname |
姓名 |
sage |
年龄 |
ssex |
性别 |
tb_course：课程表 |
|
cid |
课程编号 |
cname |
课程名 |
tid |
教师编号 |
tc_sc：成绩表 |
|
sid |
学号 |
cid |
课程编号 |
score |
成绩 |
tb_teacher：教师表 |
|
tid |
教师编号 |
tname |
教师名字 |
问题：
1、删除“002”同学的“001”课程的成绩
DELETE cid='001' FROM tc_sc WHERE sid='002';
2、检索“004”课程分数小于60，按分数降序排列的同学学号
SELECT sid='004' FROM tc_sc WHERE score<60 ORDER BY sid DESC;
3、查询两门以上不及格课程的同学的学号及其平均成绩
SELECT sid,AVG(score) FROM tc_sc WHERE sid in
(SELECT sid FROM tc_sc WHERE score<60 GROUP BY sid HAVING COUNT(sid>=2));
4、查询没学过“张三”老师讲授的任一门课程的学生姓名
SELECT * FROM tb_student s WHERE sid NOT IN(
SELECT DISTINCT sid FROM tc_sc sc
INNER JOIN tb_course c ON sc.cid =c.cid
INNER JOIN tb_teacher t ON c.tid =t.tid
WHERE t.tname ='张三')
5、检索至少选修两门课程的学生学号
SELECT sid FROM tc_sc GROUP BY sid HAVING COUNT(cid)>=2
6、统计每门课程的学生选修人数（超过10人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列
SELECT DISTINCT cid,COUNT(sid) FROM tc_sc GROUP BY cid
HAVING COUNT(sid)>10 ORDER BY cid DESC,2 ASC
7、查询每门功成绩最好的前两名
SELECT s.sid,sname,temp.cid,temp.score FROM tb_student s INNER JOIN
(SELECT tb1.* FROM tc_sc tb1 LEFT JOIN tc_sc tb2 ON tb1.cid =tb2.cid
AND tb1.score =tb2.score
GROUP BY tb1.sid,tb1.cid,tb1.score HAVING COUNT(*)<2
)
temp ON s.sid=temp.sid ORDER BY temp.cid,temp.score DESC
8、查询不同课程成绩相同的学生的学号、课程号、学生成绩
SELECT a.* FROM tc_sc a LEFT JOIN tc_sc b
ON a.cid!=b.cid WHERE a.score=b.score;
9、查询各个课程及相应的选修人数
SELECT cid,COUNT(sid) FROM tc_sc GROUP BY cid ORDER BY cid DESC;
10、查询选修“张三”老师所授课程的学生中，成绩最高的学生姓名及其成绩
SELECT s.sid,c.cid,sname,score FROM tb_student s,tc_sc tc,tb_course c,tb_teacher t
WHERE s.sid =tc.sid AND tc.cid =c.cid AND c.tid =t.tid
AND t.tname ='张三'
AND score =(SELECT MAX(score) FROM tc_sc WHERE cid=c.cid);
11、求选了课程的学生人数
SELECT DISTINCT cid,COUNT(sid) FROM tc_sc GROUP BY cid HAVING cid is NOT NULL;
12、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
SELECT tc_sc.sid,sname FROM tc_sc,tb_student WHERE tc_sc.cid='003' AND score>80 AND tc_sc.sid=tb_student.sid;
13、查询不及格的课程，并按课程号从大到小排列
SELECT cid,score FROM tc_sc HAVING score<60 ORDER BY cid DESC;
14、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；
SELECT tb_student.sname,cid,score FROM tb_student,tc_sc WHERE score>70 AND tb_student.sid =tc_sc.sid
15、查询所有学生的选课情况；
SELECT tb_student.sid,tb_student.sname,tb_student.sage,tb_student.ssex,tb_course.cname,tc_sc.score
FROM tb_student,tc_sc,tb_course WHERE tb_student.sid =tc_sc.sid AND tb_course.cid=tc_sc.cid
16、查询课程名称为“数据库”，且分数低于60的学生姓名和分数；
SELECT sname,score FROM tb_student,tb_course,tc_sc WHERE tb_course.cid=tc_sc.cid
AND tb_student.sid=tc_sc.sid AND tb_course.cname ='数据库' AND score<60 GROUP BY sname
17、查询平均成绩大于85的所有学生的学号、姓名和平均成绩；
SELECT tb_student.sid,sname,AVG(score) FROM tb_student,tc_sc WHERE tb_student.sid=tc_sc.sid
GROUP BY tb_student.sid HAVING AVG(score)>85 ORDER BY tb_student.sid ASC
18、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列；
SELECT DISTINCT cid,AVG(score) FROM tc_sc GROUP BY cid ORDER BY AVG(score) ASC,2 DESC
19、1981年出生的学生名单(注：tb_student表中Sage列的类型是datetime);
SELECT * FROM tb_student WHERE sage LIKE '1981%' GROUP BY sid
20、查询同名同性学生名单，并统计同名人数;
SELECT a.*,COUNT(a.sid) FROM tb_student a LEFT JOIN tb_student b
ON a.sname= b.sname WHERE a.sid!=b.sid
21、查询姓“张”的学生名单;
SELECT * FROM tb_student WHERE sname LIKE '张%'
22、查询男生、女生人数;
SELECT ssex,COUNT(ssex) FROM tb_student GROUP BY ssex
23、查询出只选修了一门课程的全部学生的学号和姓名;
SELECT tb_student.sid,sname FROM tb_course,tb_student,tc_sc where tb_course.cid=tc_sc.cid AND
tc_sc.sid=tb_student.sid GROUP BY tb_student.sid HAVING COUNT(tb_student.sid)=1
24、查询每门课程被选修的学生数;
SELECT cid,COUNT(sid) FROM tc_sc GROUP BY cid
25、查询各科成绩前三名的记录:(不考虑成绩并列情况);
select a.* from tc_sc a where
(select COUNT(*)from tc_sc b where b.score>a.score)<3
26、查询不同老师所教不同课程平均分从高到低显示;
SELECT tc_sc.cid,cname,count(tc_sc.cid),score FROM tc_sc,tb_course
WHERE tc_sc.cid=tb_course.cid GROUP BY tc_sc.cid
27、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示： 学生ID,,数据库,企业管理,英语,有效课程数,有效平均分;
SELECT s.sid,sname,(SELECT score FROM tc_sc sc1
WHERE sc1.sid =s.sid AND sc1.cid =(SELECT cid FROM tb_course WHERE cname ='数据库'))数据库,
(SELECT score FROM tc_sc sc2
WHERE sc2.sid =s.sid AND sc2.cid =(SELECT cid FROM tb_course WHERE cname ='企业管理'))企业管理,
(SELECT score FROM tc_sc sc3
WHERE sc3.sid =s.sid AND sc3.cid =(SELECT cid FROM tb_course WHERE cname ='英语'))英语,
COUNT(*) 课程数,AVG(sc.score) 平均分
FROM tb_student s,tc_sc sc
WHERE s.sid =sc.sid
GROUP BY s.sid;
28、查询和“1002”号的同学学习的课程完全相同的其他同学学号和姓名；
SELECT sc.sid FROM tc_sc sc,tb_student s
WHERE sc.sid =s.sid AND sc.cid IN(SELECT cid FROM tc_sc WHERE sid =’1002’)
AND sc.cid<>2
GROUP BY sid HAVING COUNT(*) =(SELECT COUNT(*) FROM tc_sc WHERE sid =’1002’);
29、把“SC”表中“张三”老师教的课的成绩都更改为此课程的平均成绩；
update tc_sc set score=(select avg(score)
from tc_sc,tb_course,tb_teacher where
tb_course.cid=tc_sc.cid and tb_course.tid=tb_teacher.tid
and tb_teacher.tname='张三') GROUP BY sid;
30、查询至少学过学号为“001”同学所有一门课的其他同学学号和姓名；
SELECT tc_sc.sid,sname FROM tc_sc,tb_student WHERE
tc_sc.sid=tb_student.sid AND
cid IN(SELECT cid FROM tc_sc WHERE sid ='001')
31、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名;
SELECT tc_sc.sid,sname FROM tc_sc,tb_student WHERE
tc_sc.sid=tb_student.sid AND
cid IN(SELECT cid FROM tc_sc WHERE sid ='1001')
32、查询没有学全所有课的同学的学号、姓名；
SELECT tc_sc.sid,sname FROM tc_sc,tb_student
WHERE tc_sc.sid=tb_student.sid GROUP BY tc_sc.sid HAVING
COUNT(tc_sc.cid)<(SELECT COUNT(cid) FROM tc_sc)
33、查询所有课程成绩小于60分的同学的学号、姓名；
SELECT tc_sc.sid,sname FROM tc_sc,tb_student WHERE
tc_sc.sid = tb_student.sid AND score<60
34、查询学过“张三”老师所教的所有课的同学的学号、姓名；
SELECT tc_sc.sid,sname FROM tb_course,tc_sc,tb_student,tb_teacher WHERE tb_course.cid =tc_sc.cid AND
tc_sc.sid =tb_student.sid AND tb_teacher.tid =tb_course.tid AND tb_teacher.tname='张三'
35、查询所有同学的学号、姓名、选课数、总成绩；
SELECT tc_sc.sid,sname,COUNT(tc_sc.cid),COUNT(score) FROM tc_sc,tb_student,tb_course
WHERE tc_sc.sid =tb_student.sid AND tc_sc.cid =tb_course.cid GROUP BY tc_sc.sid