Database / SQL Code

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

Course(Cid,Cname,Tid) 课程表

Cid,课程编号；Cname：课程名字；Tid：教师编号

SC(Sid,Cid,score) 成绩表

Sid：学号；Cid,课程编号；score：成绩

Teacher(Tid,Tname) 教师表

Tid：教师编号； Tname：教师名字

CREATE TABLE Student 
  ( 
     Sid INT PRIMARY KEY NOT NULL,
     Sname nvarchar(32) NOT NULL, 
     Sage DATETIME NOT NULL, 
     Ssex nvarchar(8) NOT NULL 
  ) 

CREATE TABLE Course 
  ( 
     Cid INT PRIMARY KEY,
     Cname nvarchar(32) NOT NULL, 
     Tid INT NOT NULL
  ) 

CREATE TABLE SC 
  ( 
     Sid INT NOT NULL, 
     Cid INT NOT NULL, 
     score INT NOT NULL,
     PRIMARY KEY(Sid , Cid)
  ) 

CREATE TABLE Teacher 
  ( 
     Tid INT PRIMARY KEY NOT NULL, 
     Tname nvarchar(16) NOT NULL 
  )

问题：

1、查询“001”课程比“002”课程成绩高的所有学生的学号；

 SELECT Sid FROM SC AS a , SC AS b
 where a.Sid = b.Sid 
 And a.Cid = "001"
 And b.Cid = "002"
 And a.score > b.score;

2、查询平均成绩大于60分的同学的学号和平均成绩；

SELECT Sid , AVG(Score) FROM SC 
GROUP BY Sid HAVING AVG(Score) > 60;

3、查询所有同学的学号、姓名、选课数、总成绩；

SELECT Sid , Sname , COUNT(SC.Cid) as ClassNum , SUM(SC.Score) As Score
FROM Student
LEFT JOIN SC
ON Student.Sid = SC.Sid 
GROUP BY Sid , Sname;

4、查询姓“李”的老师的个数；

SELECT COUNT(DISTINCT(Tname)) From Teacher WHERE Tname LIKE '李%';

5、查询没学过“叶平”老师课的同学的学号、姓名；

SELECT Sid , Sname FROM Student 
WHERE Sid NOT IN(
      SELECT DISTINCT Sid FROM SC , Course , Teacher
      WHERE SC.Cid = Course.Cid
      AND Teacher.Tid = Course.Tid
      AND Teacher.Tname = '叶平'
      )
);

6、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；

SELECT Sid , Student.Sname FROM Student , SC
WHERE Sid = SC.Sid AND EXISTS(
  Select * from SC as SC_2 where SC_2.SID = SC.SID and SC_2.Cid ='002'
);

7、查询学过“叶平”老师所教的所有课的同学的学号、姓名；

SELECT Sid , Sname FROM Student
WHERE Sid IN(
      SELECT DISTINCT Sid FROM SC
      WHERE cid IN (
              SELECT Cid FROM course
              WHERE Tid = (
                      SELECT Tid FROM Teacher
                      WHERE Tname = "叶平"
              )
      )
);

8、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；

SELECT DISTINCT Sid , Sname FROM Student , SC AS a , SC AS b
WHERE a.Sid = b.Sid 
AND a.Cid = '001'
AND b.Cid = '002'
AND a.Score > b.Score

9、查询所有课程成绩小于60分的同学的学号、姓名；

SELECT Sid , Student.Sname FROM Student , SC
WHERE Sid = SC.Sid AND Sc.Score < 60;

13、把“SC”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩；

UPDATE SC
SET Score = (SELECT AVG(a.Score) FROM SC AS a WHERE a.Cid = SC.Cid)
FROM Course , Teacher 
WHERE Teacher.Tid = Course.Tid
AND Course.Cid = SC.Cid 
AND Teacher.Tname = '叶平';

14、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 Sid , Student.Sname FROM Student , SC 
WHERE Student.Sid = SC.Sid 
AND Cid IN (SELECT Cid FROM SC WHERE Sid ='1002') 
GROUP BY Sid 
HAVING COUNT(*) = (SELECT COUNT(*) FROM SC WHERE Sid ='1002');

15、删除学习“叶平”老师课的SC表记录；

DELETE SC
FROM Course , Teacher
WHERE Course.Cid = SC.Cid 
AND Teacher.Tid = Course.Tid
AND Teacher.Tname = '叶平';

17、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 Sid as StuID ,
(SELECT score FROM SC WHERE SC.Sid = t.id AND Cname = 'Database') AS DataBaseSYS ,
(SELECT score FROM SC WHERE SC.Sid = t.Sid AND Cname ='Management') AS Management ,
(SELECT score FROM SC WHERE SC.Sid = t.Sid AND Cname ='English ') AS English ,
COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩 
FROM SC AS t 
GROUP BY Sid 
ORDER BY AVG(t.score)

18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分

SELECT a.Cid AS CourseID , a.Score AS MaxScore , b.Score AS MinScore 
FROM SC AS a , SC AS b 
WHERE a.Cid = b.Cid 
AND MaxScore = (
 SELECT MAX(c.Score) FROM SC AS c , Student
 WHERE c.Sid = Student.Sid 
 AND a.Cid = c.Cid 
 GROUP BY c.Cid
)
AND MinScore = (
 SELECT MIN(d.Score) FROM SC AS d
 WHERE b.Cid = d.Cid 
 GROUP BY d.Cid
);

19、按各科平均成绩从低到高和及格率的百分数从高到低顺序

SELECT SC.Cid , MAX(Course.Cname) , AVG(SC.SCORE) AS AVERAGE ,
100 * SUM(CASE WHEN SC.score >= 60 THEN 1 ELSE 0 END)/COUNT(*) AS PassRate
FROM SC , Course
WHERE SC.Cid = Course.Cid,
GROUP BY Cid ,
ORDER BY AVERAGE ASC, PassRate DESC;

21、查询不同老师所教不同课程平均分从高到低显示

SELECT MAX(Teacher.Tid) , MAX(Teacher.Tname) ,Course.cid , MAX(Course.Cname) ,AVG(SC.Score) AS AVERAGE
FROM SC , Teacher , Course
WHERE Teacher.Tid = Course.Tid
AND Course.Cid = SC.Cid
GROUP BY Course.Cid 
ORDER BY AVG(Score) DESC;

23、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]

SELECT Cid , Cname ,
SUM(CASE WHEN SC.score < 60 THEN 1 ELSE 0 END) AS LowerThan60
SUM(CASE WHEN SC.score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS Between60And70
SUM(CASE WHEN SC.score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS Between70And85
SUM(CASE WHEN SC.score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS Between85And100
FROM Course , SC
WHERE SC.Cid = Course.Cid
GROUP BY SC.Cid , Cname;

24、查询学生平均成绩及其名次

 SELECT 1 + (SELECT COUNT(DISTINCT AVERAGE) FROM (
     SELECT Sid , AVG(SCORE) AS AVERAGE 
     FROM SC 
     GROUP BY Sid 
 	) AS T1 WHERE AVERAGE > T2.AVERAGE) AS Rank , Sid AS StuID , 
 FROM (SELECT Sid, AVG(SCORE) AS AVERAGE 
      FROM SC
 	GROUP BY Sid     
 ) AS T2 
 ORDER BY AVERAGE DESC;

25、查询各科成绩前三名的记录:(不考虑成绩并列情况)

SELECT Sid , Cid , Score FROM SC a
WHERE SCORE IN (SELECT TOP 3 Score From SC
                WHERE a.Cid = SC.Cid
                ORDER BY Score DESC
              )
              ORDER BY Cid;

26、查询每门课程被选修的学生数

SELECT Cid ,COUNT(Sid) FROM SC GROUP BY Cid;

27、查询出只选修了一门课程的全部学生的学号和姓名

SELECT Sid , Sname , COUNT(Cid) AS numOfClass FROM Student , SC
WHERE Student.Sid = SC.Sid
GROUP BY Sid , Sname
HAVING COUNT(Cid) = 1;

28、查询男生、女生人数

SELECT COUNT(a.Ssex) AS Male FROM Student GROUP BY Ssex HAVING Ssex = '男';
SELECT COUNT(b.Ssex) AS Female FROM Student GROUP BY Ssex HAVING Ssex = '女';

29、查询姓“张”的学生名单

SELECT Sname FROM Student WHERE Sname like '张%';

30、查询同名同性学生名单，并统计同名人数

SELECT Sname , Ssex , COUNT(*) FROM Student 
GROUP BY Sname 
HAVING COUNT(*) > 1;

31、1981年出生的学生名单(注：Student表中Sage列的类型是datetime)

SELECT Sname , Sid , CONVERT(char (11),DATEPART(year,Sage) AS AGE FROM Student 
WHERE AGE = '1981';

32、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 Cid ,AVG(Score) FROM SC GROUP BY Cid ORDER BY AVG(Score), Cid DESC ;

33、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 Sid , Sname , AVG(Score) AS AVERAGE FROM Student , SC
WHERE Student.Sid = SC.Sid 
GROUP BY SC.Sid , Sname
HAVING AVG(Score) > 85;

34、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 Student , SC , Course
WHERE Student.Sid = SC.Sid
AND Course.Cid = SC.Cid
AND Course.Cname = '数据库'
AND Score < 60;

35、查询所有学生的选课情况；

SELECT Sid , Sname , Cid , Cname FROM Student , Course , SC
WHERE Student.Sid = SC.Sid
AND Course.Cid = SC.Cid;

36、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 DISTINCT Student.Sid , Student.Sname , SC.Cid , SC.Score FROM Student , SC 
WHERE SC.score >= 70 
AND SC.Sid = Student.Sid;

37、查询不及格的课程，并按课程号从大到小排列

SELECT Cid FROM SC WHERE Score < 60 ORDER BY Cid;

38、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 Sid , Sname FROM Student , SC 
WHERE Student.Sid = SC.Sid
AND SC.Cid = '003'
AND SC.Score > 80;

40、查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩

SELECT Student.Sname , Score FROM Student , SC , Course
WHERE Student.Sid = SC.Sid
AND Course.Cid = SC.Cid
AND Course.Tname = '叶平'
AND Score = (SELECT Max(Score) FROM SC WHERE Cid = SC.Cid )

41、查询各个课程及相应的选修人数

SELECT COUNT(*) FROM SC 
GROUP BY Cid;

43、查询每门功成绩最好的前两名

SELECT Sid , Cid , Score FROM SC AS a
WHERE Score IN (
  SELECT TOP 2 Score FROM SC
  WHERE a.Cid = SC.Cid
  ORDER BY Score DESC
)
ORDER BY a.Cid;

44、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，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 Cid as ClassId, COUNT(*) AS counts 
FROM SC 
GROUP BY Cid 
HAVING COUNT(*) > 10 
ORDER BY COUNT(*) DESC , Cid ASC;

45、检索至少选修两门课程的学生学号

SELECT Sid FROM SC 
GROUP BY Sid
HAVING COUNT(*) >= 2;

46、查询全部学生都选修的课程的课程号和课程名

SELECT Cid , Cname 
FROM Course 
WHERE Cid in (SELECT Cid FROM SC
              GROUP BY Cid
             );

47、查询没学过“叶平”老师讲授的任一门课程的学生姓名

SELECT Sname FROM Student
WHERE Sid NOT IN (SELECT Sid FROM SC , Course , Teacher 
               WHERE Course.Cid = SC.Cid
                AND Teacher.Tid = Course.Tid
                AND Teacher.Tname = '叶平';
               );

48、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(isnull(Score , 0)) FROM SC 
WHERE Sid in (SELECT Sid FROM SC 
              WHERE Score < 60 
              GROUP BY Sid 
              HAVING count(*) > 2
             )
             GROUP BY Sid;

49、检索“004”课程分数小于60，按分数降序排列的同学学号

SELECT Sid FROM SC
WHERE Score < 60 
AND Cid = "004" 
ORDER BY Score DESC;

50、删除“002”同学的“001”课程的成绩

DELETE From SC
WHERE Sid = "002" AND Cid = '001'