SQL數據庫面試題以及答案（50例題）

Student(Sid,Sname,Sage,Ssex)學生表 Sid：學號 Sname：學生姓名 Sage：學生年齡 Ssex：學生性別 Course(Cid,Cname,T#)課程表 Cid：課程編號 Cname：課程名稱 Tid：教師編號 SC(Sid,Cid,score)成績表 Sid：學號 Cid：課程編號 score：成績 Teacher(Tid,Tname)教師表 Tid：教師編號： Tname：教師名字

問題：

1、查詢“001”課程比“002”課程成績高的所有學生的學號

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;

2、查詢平均成績大于60分的同學的學號和平均成績

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

3、查詢所有同學的學號、姓名、選課數、總成績

select s.sid,s.sname,count_cid as 選課數, sum_score as 總成績 from student s left join (select sid,count(cid) as count_cid,sum(score) as sum_score from sc group by sid )sc on s.sid = sc.sid;

4、查詢姓‘李’的老師的個數：

select count(tname) from teacher where tname like '李%';

5、查詢沒有學過“葉平”老師可的同學的學號、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 = '葉平') );

6、查詢學過“葉平”老師所教的所有課的同學的學號、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 = '葉平')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 = '葉平') );

7、查詢學過“011”并且也學過編號“002”課程的同學的學號、姓名：

SELECT s.sid,s.sname from student as s left join sc as sc on s.sid = sc.sid where 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.sname from student as s left join sc as sc on sc.sid = s.sid where 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);

8、查詢課程編號“002”的成績比課程編號“001”課程低的所有同學的學號、姓名：

select sid,sname from (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_2 where score2<score;

9、查詢所有課程成績小于60的同學的學號、姓名：

select sid,sname from student where sid not in (select s.sid from student s,sc where s.sid=sc.sid and score>60 );select sid,sname from student s where not EXISTS ( select s.sid from sc where sc.sid = s.sid and sc.score>60);

10、查詢沒有學全所有課的同學的學號、姓名：

select s.sid,s.sname from student s ,sc sc where s.sid = sc.sid group by s.sid,s.sname having count(sc.cid)<( select count(cid) from course);select s.sid,s.sname from student s right join sc sc on s.sid = sc.sid group by s.sid,s.sname having count(sc.cid)< (select count(cid) from course);

11、查詢至少有一門課與學號為“1001”同學所學相同的同學的學號和姓名：

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

12、查詢至少學過學號為“001”同學所有一門課的其他同學學號和姓名；

13、把“SC”表中“葉平”老師教的課的成績都更改為此課程的平均成績：

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 = '葉平');

14、查詢和“1002”號的同學學習的課程完全相同的其他同學學號和姓名：

select sc_1.sid from (select cid from sc where sid='1002')a left join sc sc_1 on a.cid = sc_1.cid where 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)a left join student s on a.sid = s.sid where a.cid_str = b.cid_str and a.sid<>'1002';

15、刪除學習“葉平”老師課的SC表記錄：

delete from sc WHERE cid in ( select c.cid from course c LEFT JOIN teacher t on c.tid=t.tid where t.tname = '葉平');

16、向SC表中插入一些記錄，這些記錄要求符合以下條件：沒有上過編號“003”課程的同學學號、002號課的平均成績：

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');

17、按平均成績從高到低顯示所有學生的“數據庫”、“企業管理”、“英語”三門的課程成績，按如下形式顯示：學生ID，數據庫，企業管理，英語，有效課程數，有效平均分：

select sid as 學生id, (SELECT score from sc where sc.sid = t.sid and cid='004') as 數據庫, (select score from sc where sc.sid = t.sid and cid='001') as 企業管理, (select score from sc where sc.sid = t.sid and cid='015') as 英語, count(cid) as 有效課程數, avg(t.score) as 平均成績 from sc as t group by sid order by avg(t.score);

18、查詢各科成績最高和最低的分：以如下的形式顯示：課程ID，最高分，最低分

select l.cid as 課程id,l.score as 最高分, r.score as 最低分 from sc l,sc r where l.cid = r.cid and 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 課程id,max(score) as 最高分, min(score) as 最低分 from sc group by cid;

19、按各科平均成績從低到高和及格率的百分數從高到低順序：

SELECT t.cid as 課程號, c.cname as 課程名, COALESCE(avg(score),0) as 平均成績, 100*sum(case when COALESCE(score,0)>=60 then 1 else 0 END)/count(*) as 及格百分數 from sc t left join course c on t.cid = c.cid group by t.cid order by 100*sum(case when COALESCE(score,0)>=60 then 1 else 0 END)/count(*);

20、查詢如下課程平均成績和及格率的百分數(用”1行”顯示): 企業管理（001），馬克思（002），OO&UML （003），數據庫（004）：

21、查詢不同老師所教不同課程平均分從高到低顯示：

select t.tid as 教師id, t.tname as 教師姓名, sc.cid as 課程id, avg(score) as 平均成績 from sc as sc LEFT JOIN course c on sc.cid = c.cid left join teacher t on c.tid = t.tid group by sc.cid order by avg(sc.score) desc;

22、查詢如下課程成績第3名到第6名的學生成績單：企業管理(001)，馬克思(002)，UML(003)，數據庫(004)：

23、統計下列各科成績，各分數段人數：課程ID，課程名稱，[100-85],[85-70],[70-60],[ 小于60] ：

select sc.cid as 課程id,cname as 課程名稱, 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 c on sc.cid = c.cid group by sc.cid;

24、查詢學生平均成績及其名次：

select 1+(select count(distinct 平均成績) from (select sid,avg(score) as 平均成績 from sc group by sid)t1 where 平均成績>t2.平均成績) as 名次, sid as 學生學號,平均成績 from (select sid,avg(score) 平均成績 from sc group by sid) as t2 order by 平均成績 desc;

25、查詢各科成績前三名的記錄（不考慮成績并列情況）：

select sid,cid,score from sc sc_1 where ( 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 );

26、查詢每門課程被選修的學生數：

select cid, count(sid) from sc group by cid;

27、查詢出只選修一門課程的全部學生的學號和姓名：

select sc.sid,s.sname, count(sc.cid) as 課程數 from sc as sc LEFT JOIN student as s on sc.sid = s.sid group by sc.sid having count(sc.cid)=1;

28、查詢男生、女生人數：

select count(ssex) as 男生人數 from student group by ssex having ssex = '男'; select count(2) from student where ssex = '女';

29、查詢姓“張”的學生名單：

select sid,sname from student where sname like '張%';

30、查詢同名同姓的學生名單，并統計同名人數：

select sname,count(8) from student group by sname having count(8)>1;

31、1981年出生的學生名單（注：student表中sage列的類型是datetime）:

32、查詢平均成績大于85的所有學生的學號、姓名和平均成績：

select s.sname,sc.sid,avg(sc.score) as 平均成績 from sc as sc left join student as s on sc.sid = s.sid group by sc.sid having avg(sc.score)>85;

33、查詢每門課程的平均成績，結果按平均成績升序排序，平均成績相同時，按課程號降序排列：

select cid,avg(score) from sc group by cid order by avg(score),cid desc;

34、查詢課程名稱為“數據庫”，且分數低于60的學生名字和分數：

select c.cname,s.sid,s.sname,sc.score from course c left join sc on sc.cid = c.cid LEFT JOIN student s on s.sid = sc.sid where c.cname = '數據庫' and sc.score<60;

35、查詢所有學生的選課情況：

select sc.sid,sc.cid,s.sname,c.cname from sc LEFT JOIN course c on sc.cid = c.cid left join student s on sc.sid = s.sid;

36、查詢任何一門課程成績在70分以上的姓名、課程名稱和分數：

select distinct s.sid,s.sname,sc.cid,sc.score from sc left join student s on sc.sid = s.sid left join course c on sc.cid = c.cid where sc.score>70;

37、查詢不及格的課程，并按課程號從大到小的排列：

select cid from sc where score<60 ORDER BY cid;

38、查詢課程編號為“003”且課程成績在80分以上的學生的學號和姓名：

select sc.sid,s.sname from sc left join student s on sc.sid = s.sid where sc.cid = '003' and sc.score>80;

39、求選了課程的學生人數：

select count(2) from (select distinct sid from sc)a;

40、查詢選修“葉平”老師所授課程的學生中，成績最高的學生姓名及其成績：

select s.sname,sc.score from sc sc left join student s on sc.sid = s.sid left join course c on sc.cid = c.cid left join teacher t on c.tid = t.tid where t.tname = '葉平' and sc.score = ( select max(score) from sc sc_1 where sc.cid = sc_1.cid);

41、查詢各個課程及相應的選修人數：

select cid,count(*) from sc group by cid;

42、查詢不同課程成績相同的學生和學號、課程號、學生成績：

select DISTINCT a.sid,a.cid,a.score from sc as a ,sc as b where a.score = b.score and a.cid <> b.cid;

43、查詢每門課程成績最好的前兩名：

44、統計每門課程的學生選修人數(超過10人的課程才統計)。要求輸出課程號和選修人數，查詢結果按人數降序排序，若人數相同，按課程號升序排序：

select cid as 課程號,count(8) as 選修人數 from sc group by cid HAVING count(sid)>10 order by count(8) desc,cid;

45、檢索至少選修兩門課程的學生學號：

select sid from sc group by sid having count(8)>=2;

46、查詢全部學生選修的課程和課程號和課程名：

select cid,cname from course where cid in (select cid from sc group by cid);

47、查詢沒學過”葉平”老師講授的任一門課程的學生姓名：

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='葉平' );

48、查詢兩門以上不及格課程的同學的學號以及其平均成績：

select sid,avg(COALESCE(score,0)) from sc where sid in (select sid from sc where score<60 group by sid having count(8)>2 ) group by sid;

49、檢索“004”課程分數小于60，按分數降序排列的同學學號：

select sid,score from sc where cid='004' and score<60 order by score desc;

50、刪除“002”同學的“001”課程的成績：

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

總結

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