数据库常见面试题总结（通俗易懂）

淡淡的烟草味﹌ 2022-06-14 05:55 269阅读 0赞

Student(S\#,Sname,Sage,Ssex) 学生表

Course(C\#,Cname,T\#) 课程表  
SC(S\#,C\#,score) 成绩表  
Teacher(T\#,Tname) 教师表  
   
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 0END) 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 0END) 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 0END) 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';