常见SQL数据库面试题和答案(一)
Student(S#,Sname,Sage,Ssex) 学生表 S#：学号；Sname：学生姓名；Sage：学生年龄；Ssex：学生性别
Course(C#,Cname,T#) 课程表 C#,课程编号；Cname：课程名字；T#：教师编号
SC(S#,C#,score) 成绩表 S#：学号；C#,课程编号；score：成绩
Teacher(T#,Tname) 教师表 T#：教师编号； Tname：教师名字
问题：
1、查询“001”课程比“002”课程成绩高的所有学生的学号；
select # from (select s#,score from SC where C#='001') a,(select s#,score
from SC where C#='002') b
where > and #=#;
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 #,,count#),sum(score)
from Student left Outer join SC on #=#
group by #,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 #,
from Student
where S# not in (select distinct( #) from SC,Course,Teacher where #=# and #=# and ='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 #, from Student,SC where #=# and #='001'and exists( Select * from SC as SC_2 where #=# and #='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 #=# and #=# and ='叶平' group by S# having count#)=(select count(C#) from Course,Teacher where #=# 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 #,,score ,(select score from SC SC_2 where #=# and #='002') score2
from Student,SC where #=# 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 # from Student,SC where #=# and score>60);
10、查询没有学全所有课的同学的学号、姓名；
select #,
from Student,SC
where #=# group by #, 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 #=# 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 #,Sname
from Student,SC
where #=# 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
from SC SC_2
where #=# ) from Course,Teacher where #=# and #=# and ='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 #=# and #= # 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 #=# AND C#='004') AS 数据库
,(SELECT score FROM SC WHERE #=# AND C#='001') AS 企业管理
,(SELECT score FROM SC WHERE #=# AND C#='006') AS 英语
,COUNT(*) AS 有效课程数, AVG AS 平均成绩
FROM SC AS t
GROUP BY S#
ORDER BY avg
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 # As 课程ID, AS 最高分, AS 最低分
FROM SC L ,SC AS R
sql查询面试题 WHERE # = # and
= (SELECT MAX
FROM SC AS IL,Student AS IM
WHERE # = # and #=#
GROUP BY #)
AND
= (SELECT MIN
FROM SC AS IR
WHERE # = #
GROUP BY #
);
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 # AS 课程号,maxAS 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 #=#
GROUP BY #
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
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