常见的50道数据库面试题

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50个常用sql语句

学生表Student(S#,Sname,Sage,Ssex)

课程表 Course(C#,Cname,T#)

成绩表 SC(S#,C#,score)

教师表Teacher(T#,Tname)

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.scoreand 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¨ （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.scorefrom 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,scorefrom 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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