简明现代魔法 -> 数据库技术 -> 从一个问题中看常用的SQL语句

从一个问题中看常用的SQL语句

2009-11-06

数据库如下:

问题:

1、查询“001”课程比“002”课程成绩高的所有学生的学号

select a.S# from (select s#,score from SC where C#='001') a,(select s#,score 
from SC where C#='002') b 
where a.score>b.score and a.s#=b.s#;

2、查询平均成绩大于60分的同学的学号和平均成绩;

select S#,avg(score) 
from sc 
group by S# having avg(score) >60; 

3、查询所有同学的学号、姓名、选课数、总成绩;

select Student.S#,Student.Sname,count(SC.C#),sum(score) 
from Student left Outer join SC on Student.S#=SC.S# 
group by Student.S#,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 Student.S#,Student.Sname 
from Student 
where S# not in (select distinct( SC.S#) from SC,Course,Teacher 
where SC.C#=Course.C# and Teacher.T#=Course.T# 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 Student.S#,Student.Sname from Student,SC 
where Student.S#=SC.S# and SC.C#='001'and 
exists( Select * from SC as SC_2 where SC_2.S#=SC.S# and SC_2.C#='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 S#,Sname 
from Student 
where S# in (select S# from SC ,Course ,Teacher 
where SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname='叶平' 
group by S# having count(SC.C#)=(select count(C#) from Course,Teacher 
where Teacher.T#=Course.T# and 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 S#,Sname from (select Student.S#,Student.Sname,score ,(select score from SC SC_2 
where SC_2.S#=Student.S# and SC_2.C#='002') score2 
from Student,SC where Student.S#=SC.S# and C#='001') S_2 where score2 <score;

9、查询所有课程成绩小于60分的同学的学号、姓名;

select S#,Sname 
from Student 
where S# not in (select Student.S# from Student,SC where S.S#=SC.S# and score>60);

10、查询没有学全所有课的同学的学号、姓名;

select Student.S#,Student.Sname 
from Student,SC 
where Student.S#=SC.S# 
group by Student.S#,Student.Sname having count(C#) <(select count(C#) from Course); 

11、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 S#,Sname from Student,SC 
where Student.S#=SC.S# and C# in select C# from SC where S#='1001'; 

12、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 distinct SC.S#,Sname 
from Student,SC 
where Student.S#=SC.S# and C# in (select C# from SC where S#='001'); 

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(SC_2.score) 
from SC SC_2 
where SC_2.C#=SC.C# ) from Course,Teacher 
where Course.C#=SC.C# and Course.T#=Teacher.T# 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 S# from SC where C# in (select C# from SC where S#='1002') 
group by S# having count(*)=(select count(*) from SC where S#='1002'); 

15、删除学习“叶平”老师课的SC表记录;

Delect SC 
from course ,Teacher 
where Course.C#=SC.C# and Course.T#= Teacher.T# and Tname='叶平';

16、向SC表中插入一些记录,这些记录要求符合以下条件:没有上过编号“003”课程的同学学号、2、号课的平均成绩;

Insert SC select S#,'002',(Select avg(score) 
from SC where C#='002') from Student 
where S# not in (Select S# from SC where C#='002');

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 S# as 学生ID 
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='004') AS 数据库 
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='001') AS 企业管理 
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='006') AS 英语 
,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩 
FROM SC AS t 
GROUP BY S# 
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 L.C# As 课程ID,L.score AS 最高分,R.score AS 最低分 
FROM SC L ,SC AS R 
WHERE L.C# = R.C# and 
L.score = (SELECT MAX(IL.score) 
FROM SC AS IL,Student AS IM 
WHERE L.C# = IL.C# and IM.S#=IL.S# 
GROUP BY IL.C#) 
AND 
R.Score = (SELECT MIN(IR.score) 
FROM SC AS IR 
WHERE R.C# = IR.C# 
GROUP BY IR.C# 
); 

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 t.C# AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩 
,100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数 
FROM SC T,Course 
where t.C#=course.C# 
GROUP BY t.C# 
ORDER BY 100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC

20、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理(001),马克思(002),OO&UML (003),数据库(004)

SELECT SUM(CASE WHEN C# ='001' THEN score ELSE 0 END)/SUM(CASE C# WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分 
,100 * SUM(CASE WHEN C# = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数 
,SUM(CASE WHEN C# = '002' THEN score ELSE 0 END)/SUM(CASE C# WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分 
,100 * SUM(CASE WHEN C# = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数 
,SUM(CASE WHEN C# = '003' THEN score ELSE 0 END)/SUM(CASE C# WHEN '003' THEN 1 ELSE 0 END) AS UML平均分 
,100 * SUM(CASE WHEN C# = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '003' THEN 1 ELSE 0 END) AS UML及格百分数 
,SUM(CASE WHEN C# = '004' THEN score ELSE 0 END)/SUM(CASE C# WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分 
,100 * SUM(CASE WHEN C# = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '004' THEN 1 ELSE 0 END) AS 数据库及格百分数 
FROM SC 

21、查询不同老师所教不同课程平均分从高到低显示

SELECT max(Z.T#) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.C# AS 课程ID,MAX(C.Cname) AS 课程名称,AVG(Score) AS 平均成绩 
FROM SC AS T,Course AS C ,Teacher AS Z 
where T.C#=C.C# and C.T#=Z.T# 
GROUP BY C.C# 
ORDER BY AVG(Score) DESC

22、查询如下课程成绩第 3 名到第 6 名的学生成绩单:企业管理(001),马克思(002),UML (003),数据库(004) [学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩

SELECT DISTINCT top 3 
SC.S# As 学生学号, 
Student.Sname AS 学生姓名 , 
T1.score AS 企业管理, 
T2.score AS 马克思, 
T3.score AS UML, 
T4.score AS 数据库, 
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 总分 
FROM Student,SC LEFT JOIN SC AS T1 
ON SC.S# = T1.S# AND T1.C# = '001' 
LEFT JOIN SC AS T2 
ON SC.S# = T2.S# AND T2.C# = '002' 
LEFT JOIN SC AS T3 
ON SC.S# = T3.S# AND T3.C# = '003' 
LEFT JOIN SC AS T4 
ON SC.S# = T4.S# AND T4.C# = '004' 
WHERE student.S#=SC.S# and 
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) 
NOT IN 
(SELECT 
DISTINCT 
TOP 15 WITH TIES 
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) 
FROM sc 
LEFT JOIN sc AS T1 
ON sc.S# = T1.S# AND T1.C# = 'k1' 
LEFT JOIN sc AS T2 
ON sc.S# = T2.S# AND T2.C# = 'k2' 
LEFT JOIN sc AS T3 
ON sc.S# = T3.S# AND T3.C# = 'k3' 
LEFT JOIN sc AS T4 
ON sc.S# = T4.S# AND T4.C# = 'k4' 
ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) 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 SC.C# as 课程ID, Cname as 课程名称 
,SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 - 85] 
,SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 - 70] 
,SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 - 60] 
,SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS [60 -] 
FROM SC,Course 
where SC.C#=Course.C# 
GROUP BY SC.C#,Cname;

24、查询学生平均成绩及其名次

SELECT 1+(SELECT COUNT( distinct 平均成绩) 
FROM (SELECT S#,AVG(score) AS 平均成绩 
FROM SC 
GROUP BY S# 
) AS T1 
WHERE 平均成绩 > T2.平均成绩) as 名次, 
S# as 学生学号,平均成绩 
FROM (SELECT S#,AVG(score) 平均成绩 
FROM SC 
GROUP BY S# 
) AS T2 
ORDER BY 平均成绩 desc; 

25、查询各科成绩前三名的记录:(不考虑成绩并列情况)

SELECT t1.S# as 学生ID,t1.C# as 课程ID,Score as 分数 
FROM SC t1 
WHERE score IN (SELECT TOP 3 score 
FROM SC 
WHERE t1.C#= C# 
ORDER BY score DESC 
) 
ORDER BY t1.C#;

26、查询每门课程被选修的学生数

select c#,count(S#) from sc group by C#; 

27、查询出只选修了一门课程的全部学生的学号和姓名

select SC.S#,Student.Sname,count(C#) AS 选课数 
from SC ,Student 
where SC.S#=Student.S# group by SC.S# ,Student.Sname having count(C#)=1; 

28、查询男生、女生人数

Select count(Ssex) as 男生人数 from Student group by Ssex having Ssex='男'; 
Select count(Ssex) as 女生人数 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,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, CONVERT(char (11),DATEPART(year,Sage)) as age 
from student 
where CONVERT(char(11),DATEPART(year,Sage))='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 C#,Avg(score) from SC group by C# order by Avg(score),C# 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 Sname,SC.S# ,avg(score) 
from Student,SC 
where Student.S#=SC.S# group by SC.S#,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,isnull(score,0) 
from Student,SC,Course 
where SC.S#=Student.S# and SC.C#=Course.C# and Course.Cname='数据库'and score <60; 

35、查询所有学生的选课情况;

SELECT SC.S#,SC.C#,Sname,Cname 
FROM SC,Student,Course 
where SC.S#=Student.S# and SC.C#=Course.C# ;

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.S#,student.Sname,SC.C#,SC.score 
FROM student,Sc 
WHERE SC.score>=70 AND SC.S#=student.S#; 

37、查询不及格的课程,并按课程号从大到小排列

select c# from sc where scor e <60 order by C# ;

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 SC.S#,Student.Sname from SC,Student 
where SC.S#=Student.S# and Score>80 and C#='003';

39、求选了课程的学生人数

select count(*) from sc; 

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 C,Teacher 
where Student.S#=SC.S# and SC.C#=C.C# and C.T#=Teacher.T# and Teacher.Tname='叶平' 
and SC.score=(select max(score)from SC where C#=C.C# ); 

41、查询各个课程及相应的选修人数

select count(*) from sc group by C#; 

42、查询不同课程成绩相同的学生的学号、课程号、学生成绩

select distinct A.S#,B.score from SC A ,SC B where A.Score=B.Score and A.C# <>B.C# ;

43、查询每门功成绩最好的前两名

SELECT t1.S# as 学生ID,t1.C# as 课程ID,Score as 分数 
FROM SC t1 
WHERE score IN (SELECT TOP 2 score 
FROM SC 
WHERE t1.C#= C# 
ORDER BY score DESC 
) 
ORDER BY t1.C#;

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 C# as 课程号,count(*) as 人数 
from sc 
group by C# 
order by count(*) desc,c# 

45、检索至少选修两门课程的学生学号

select S# 
from sc 
group by s# 
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 C#,Cname 
from Course 
where C# in (select c# from sc group by c#) 

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 S# not in (select S# from Course,Teacher,SC 
where Course.T#=Teacher.T# and SC.C#=course.C# and 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 S#,avg(isnull(score,0)) from SC 
where S# in (select S# from SC where score <60 
group by S# having count(*)>2)group by S#;

49、检索“004”课程分数小于60,按分数降序排列的同学学号

select S# from SC where C#='004'and score <60 order by score desc;  

50、删除“002”同学的“001”课程的成绩

delete from Sc where S#='001'and C#='001'; 
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