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SQL数据库面试题以及答案（50例题）

SQL数据库面试题以及答案（50例题）

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,T#)课程表Cid：课程编号Cname：课程名称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 
 
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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.sid from (select sid,score from sc where cid='001')a,(select sid,score from sc where cid='002')b where a.sid = b.sid and a.score>b.score; 
 
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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 scgroup by sid having avg(score)>60; 
 
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3、查询所有同学的学号、姓名、选课数、总成绩

select s.sid,s.sname,count_cid as 选课数, sum_score  as 总成绩from student sleft join (select sid,count(cid) as count_cid,sum(score) as sum_score from sc group by sid )scon s.sid = sc.sid; 
 
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4、查询姓‘李’的老师的个数：

select count(tname)from teacher where tname like '李%'; 
 
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5、查询没有学过“叶平”老师可的同学的学号、姓名：

select s.sid,s.sname from student as s where s.sid not in (    select DISTINCT sid     from sc as sc     where sc.cid in (        select cid         from course as c         left join teacher as t on c.tid = t.tid         where t.tname = '叶平')); 
 
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6、查询学过“叶平”老师所教的所有课的同学的学号、姓名：

select s.sid,s.sname from student as s where s.sid in (    select distinct sc.sid   from sc as sc   where sc.cid in (    select cid     from course as c     left join teacher as t on c.tid = t.tid     where t.tname = '叶平')        group by sc.sid     HAVING count(cid)=    (select count(cid)      from course as c left join teacher as t on c.tid = t.tid      where t.tname = '叶平')); 
 
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7、查询学过“011”并且也学过编号“002”课程的同学的学号、姓名：

SELECT s.sid,s.sname from student as s left join sc as sc on s.sid = sc.sidwhere sc.cid = '001'and EXISTS(  select * from sc as sc_2   where sc.sid = sc_2.sid   and sc_2.cid='002');select s.sid,s.snamefrom student as s left join sc as sc on sc.sid = s.sidwhere sc.cid = '001'and s.sid in (  select sid from sc as sc_2   where sc_2.cid='002'   and sc_2.sid = sc.sid); 
 
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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 sid,snamefrom (select student.sid,student.sname,score,     (select score from sc as sc_2       where sc_2.sid = student.sid       and sc_2.cid = '002') as score2       from student,sc       where student.sid=sc.sid and cid = '001') s_2where score2

9、查询所有课程成绩小于60的同学的学号、姓名：

select sid,snamefrom studentwhere sid not in (select s.sid from student s,sc where s.sid=sc.sid and score>60 );select sid,snamefrom student swhere not EXISTS (select s.sid from sc where sc.sid = s.sid and sc.score>60); 
 
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10、查询没有学全所有课的同学的学号、姓名：

select s.sid,s.snamefrom student s ,sc sc where s.sid = sc.sidgroup by s.sid,s.snamehaving count(sc.cid)<(select count(cid) from course);select s.sid,s.snamefrom student s right join sc sc on s.sid = sc.sidgroup by s.sid,s.snamehaving count(sc.cid)<(select count(cid) from course); 
 
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11、查询至少有一门课与学号为“1001”同学所学相同的同学的学号和姓名：

select student.sid,snamefrom student,sc where student.sid = sc.sidand cid in (select cid from sc where sid='1001');select s.sid,s.snamefrom sc sc left join student as son sc.sid = s.sidwhere sc.cid in (select cid from sc where sid='1001');select sc_1.sid,s.snamefrom sc sc_1 left join student as son sc_1.sid = s.sidwhere exists (select sc_2.cid from sc as sc_2 where sc_1.cid = sc_2.cid and sc_2.sid = '1001'); 
 
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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；

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.cid = sc.cid)where cid in (select c.cid from course c left join teacher t on t.tid = c.tid where t.tname = '叶平'); 
 
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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 sc_1.sid from (select cid from sc where sid='1002')aleft join sc sc_1 on a.cid = sc_1.cidwhere sc_1.sid<>'1002' group by sc_1.sid having count(sc_1.cid) = (select count(cid) from sc where sid='1002');select a.sid,s.sname from (select sid,GROUP_CONCAT(cid order by cid separator ',') as cid_str from sc where sid='1002')b,(select sid,GROUP_CONCAT(cid order by cid separator ',') as cid_str from sc group by sid)aleft join student s on a.sid = s.sidwhere a.cid_str = b.cid_str and a.sid<>'1002'; 
 
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15、删除学习“叶平”老师课的SC表记录：

delete from sc WHEREcid in (select c.cid from course c LEFT JOIN teacher t on c.tid=t.tid where t.tname = '叶平'); 
 
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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、002号课的平均成绩：

insert into sc select sid,'002',(select avg(score) from sc where cid='0022')from student where sid not in (select sid from sc where cid='002'); 
 
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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 学生id,(SELECT score from sc where sc.sid = t.sid and cid='004') as 数据库,(select score from sc where sc.sid = t.sid and cid='001') as 企业管理,(select score from sc where sc.sid = t.sid and cid='015') as 英语,count(cid) as 有效课程数, avg(t.score) as 平均成绩from sc as t group by sidorder by avg(t.score); 
 
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18、查询各科成绩最高和最低的分：以如下的形式显示：课程ID，最高分，最低分

select l.cid as 课程id,l.score as 最高分,r.score as 最低分from sc l,sc rwhere l.cid = r.cidand l.score = (select max(t.score) from sc t where l.cid = t.cid group by t.cid)and r.score = (select min(t.score) from sc t where r.cid = t.cid group by t.cid)order by l.cid;select cid as 课程id,max(score) as 最高分,min(score) as 最低分from sc group by cid; 
 
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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.cid as 课程号,c.cname as 课程名,COALESCE(avg(score),0) as 平均成绩,100*sum(case when COALESCE(score,0)>=60 then 1 else 0 END)/count(*) as 及格百分数from sc tleft join course c on t.cid = c.cidgroup by t.cidorder by 100*sum(case when COALESCE(score,0)>=60 then 1 else 0 END)/count(*); 
 
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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）：

21、查询不同老师所教不同课程平均分从高到低显示：

select t.tid as 教师id,t.tname as 教师姓名,sc.cid as 课程id,avg(score) as 平均成绩from sc as scLEFT JOIN course c on sc.cid = c.cidleft join teacher t on c.tid = t.tidgroup by sc.cid order by avg(sc.score) desc; 
 
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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)：

23、统计下列各科成绩，各分数段人数：课程ID，课程名称，[100-85],[85-70],[70-60],[ 小于60] ：

select sc.cid 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 '[60-0]'from sc as sc left join course as con sc.cid = c.cidgroup by sc.cid; 
 
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24、查询学生平均成绩及其名次：

select 1+(select count(distinct 平均成绩) from (select sid,avg(score) as 平均成绩 from sc group by sid)t1 where 平均成绩>t2.平均成绩) as 名次,sid as 学生学号,平均成绩 from (select sid,avg(score) 平均成绩 from sc group by sid) as t2order by 平均成绩 desc; 
 
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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,scorefrom sc sc_1where (select count(3) from sc sc_2 where sc_1.cid = sc_2.cid and sc_2.score>=sc_1.score)<=2 order by sc_1.cid); 
 
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26、查询每门课程被选修的学生数：

select cid, count(sid)from sc group by cid; 
 
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27、查询出只选修一门课程的全部学生的学号和姓名：

select sc.sid,s.sname,count(sc.cid) as 课程数from sc as scLEFT JOIN student as son sc.sid = s.sidgroup by sc.sidhaving count(sc.cid)=1; 
 
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28、查询男生、女生人数：

select count(ssex) as 男生人数from studentgroup by ssexhaving ssex = '男';select count(2) from studentwhere ssex = '女'; 
 
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29、查询姓“张”的学生名单：

select sid,snamefrom student where sname like '张%'; 
 
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30、查询同名同姓的学生名单，并统计同名人数：

select sname,count(8)from student group by snamehaving count(8)>1; 
 
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31、1981年出生的学生名单（注：student表中sage列的类型是datetime）:

32、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 s.sname,sc.sid,avg(sc.score) as 平均成绩from sc as scleft join student as s on sc.sid = s.sidgroup by sc.sid having avg(sc.score)>85; 
 
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33、查询每门课程的平均成绩，结果按平均成绩升序排序，平均成绩相同时，按课程号降序排列：

select cid,avg(score)from sc group by cidorder by avg(score),cid desc; 
 
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34、查询课程名称为“数据库”，且分数低于60的学生名字和分数：

select c.cname,s.sid,s.sname,sc.scorefrom course cleft join sc on sc.cid = c.cidLEFT JOIN student s on s.sid = sc.sidwhere c.cname = '数据库' and sc.score<60; 
 
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35、查询所有学生的选课情况：

select sc.sid,sc.cid,s.sname,c.cnamefrom sc LEFT JOIN course c on sc.cid = c.cidleft join student s on sc.sid = s.sid; 
 
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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 s.sid,s.sname,sc.cid,sc.scorefrom sc left join student s on sc.sid = s.sidleft join course c on sc.cid = c.cidwhere sc.score>70; 
 
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37、查询不及格的课程，并按课程号从大到小的排列：

select cidfrom sc where score<60ORDER BY cid; 
 
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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.sid,s.sname from sc left join student s on sc.sid = s.sidwhere sc.cid = '003' and sc.score>80; 
 
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39、求选了课程的学生人数：

select count(2) from (select distinct sid from sc)a; 
 
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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 s.sname,sc.scorefrom sc sc left join student s on sc.sid = s.sidleft join course c on sc.cid = c.cidleft join teacher t on c.tid = t.tidwhere t.tname = '叶平'and sc.score = (select max(score) from sc sc_1 where sc.cid = sc_1.cid); 
 
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41、查询各个课程及相应的选修人数：

select cid,count(*) from sc group by cid; 
 
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42、查询不同课程成绩相同的学生和学号、课程号、学生成绩：

select DISTINCT a.sid,a.cid,a.scorefrom sc as a ,sc as b where a.score = b.scoreand a.cid <> b.cid; 
 
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43、查询每门课程成绩最好的前两名：

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序，若人数相同，按课程号升序排序：

select cid as 课程号,count(8) as 选修人数from scgroup by cidHAVING count(sid)>10order by count(8) desc,cid; 
 
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45、检索至少选修两门课程的学生学号：

select sidfrom scgroup by sidhaving count(8)>=2; 
 
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46、查询全部学生选修的课程和课程号和课程名：

select cid,cnamefrom course where cid in (select cid from sc group by cid); 
 
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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.tid = teacher.tid and sc.cid = course.cid     and teacher.tname='叶平'); 
 
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48、查询两门以上不及格课程的同学的学号以及其平均成绩：

select sid,avg(COALESCE(score,0))from scwhere sid in (    select sid     from sc     where score<60     group by sid     having count(8)>2)group by sid; 
 
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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,scorefrom scwhere cid='004'and score<60order by score desc; 
 
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50、删除“002”同学的“001”课程的成绩：

delete from sc where sid = '002' and cid = '001'; 
 
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