SQL笔试题：下面是学生表（student）的结构说明
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字段名称
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字段解释
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字段类型
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字段长度
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约束
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s_id
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学号
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字符
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10
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PK
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s_name
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学生姓名
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字符
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50
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Not null
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s_age
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学生年龄
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数值
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3
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Not null
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s-sex
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学生性别
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字符（男：1女：0）
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1
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Not null
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下面是教师表（Teacher ）的结构说明
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字段名称
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字段解释
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字段类型
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字段长度
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约束
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t_id
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教师编号
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字符
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10
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PK
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t_name
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教师名字
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字符
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50
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Not null
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下面是课程表（Course）的结构说明
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字段名称
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字段解释
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字段类型
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字段长度
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约束
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c_id
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课程编号
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字符
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10
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PK
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c_name
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课程名字
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字符
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50
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Not null
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t_id
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教师编号
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字符
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10
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Not null
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下面是成绩表（SC）的结构说明
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字段名称
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字段解释
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字段类型
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字段长度
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约束
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s_id
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学号
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字符
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10
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PK
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c_id
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课程编号
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字符
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10
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Not null
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score
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成绩
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数值
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3
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Not null
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1、查询“001”课程比“002”课程成绩高的所有学生的学号；
select a.s_id from (select s_id,score from SC where C_ID='001') a,(select s_id,score
from SC where C_ID='002') b
where a.score>b.score and a.s_id=b.s_id;
2、查询平均成绩大于60分的同学的学号和平均成绩；
select S_ID,avg(score)
from sc
group by S_ID 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_ID,Student.Sname,count(SC.C_ID),sum(score)
from Student left Outer join SC on Student.S_ID=SC.S_ID
group by Student.S_ID,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_ID,Student.Sname
from Student
where S_ID not in (select distinct( SC.S_ID) from SC,Course,Teacher where SC.C_ID=Course.C_ID 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；
elect Student.S_ID,Student.Sname from Student,SC where Student.S_ID=SC.S_ID and SC.C_ID='001'and exists( Select * from SC as SC_2 where SC_2.S_ID=SC.S_ID and SC_2.C_ID='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_ID,Sname
from Student
where S_ID in (select S_ID from SC ,Course ,Teacher where SC.C_ID=Course.C_ID and Teacher.T#=Course.T# and Teacher.Tname='叶平' group by S_ID having count(SC.C_ID)=(select count(C_ID) 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_ID,Sname from (select Student.S_ID,Student.Sname,score ,(select score from SC SC_2 where SC_2.S_ID=Student.S_ID and SC_2.C_ID='002') score2
from Student,SC where Student.S_ID=SC.S_ID and C_ID='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_ID,Sname
from Student
where S_ID not in (select S.S_ID from Student AS S,SC where S.S_ID=SC.S_ID and score>60);
10、查询没有学全所有课的同学的学号、姓名；
select Student.S_ID,Student.Sname
from Student,SC
where Student.S_ID=SC.S_ID group by Student.S_ID,Student.Sname having count(C_ID) <(select count(C_ID) 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 distinct S_ID,Sname from Student,SC where Student.S_ID=SC.S_ID and SC.C_ID in (select C_ID from SC where S_ID='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_ID,Sname
from Student,SC
where Student.S_ID=SC.S_ID and C_ID in (select C_ID from SC where S_ID='001');