一.表名和字段
–1.学生表
Student(s_id,s_name,s_birth,s_sex) --学生编号,学生姓名, 出生年月,学生性别
–2.课程表
Course(c_id,c_name,t_id) – --课程编号, 课程名称, 教师编号
–3.教师表
Teacher(t_id,t_name) --教师编号,教师姓名
–4.成绩表
Score(s_id,c_id,s_score) --学生编号,课程编号,分数
1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数
Select s_name as 学生姓名,s_score as 学生成绩
From student as s
Inner join score as sc on s.s_id=sc.s_id
Where （select s_score from score where c_id=’01’）>(select s_score from score where c_id=’02’)
2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数
Select s_name as 学生姓名,s_score as 学生成绩
From student
From student as s
Inner join score as sc on s.s_id=sc.s_id
Where （select s_score from score where c_id=’01’）<(select s_score from score where c_id=’02’)
3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩
Select s.s_id as 学生id，s_name as 学生姓名，avg(sc.s_score)as 学生成绩
From student as s
Inner join score as sc
On s.s_id=sc,s_id
Where avg(sc.score)>60
4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩
-- (包括有成绩的和无成绩的)
Select s.s_id as 学生id，s_name as 学生姓名，avg(sc.s_score)as 学生成绩
From student as s
Inner join score as sc
On s.s_id=sc,s_id
Where avg(sc.score)<60
5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩
Select s.s_id as 学生编号，s.s_name as 学生姓名，count(sc.c_id)as 选课总数，sum（sc.s_score）as 所有课程的总成绩
From stuednt as s
Inner join score sc on s.s_id=sc,s_id
Group by s.s_id
6、查询"李"姓老师的数量
select count（t_name）as 李姓老师的数量
From teacher
Where t_name like ‘李%’
7、查询学过"张三"老师授课的同学的信息
Select*
From student
Where s_id in(
select t_id from teacher as t
inner join course as c on t.t_id=c.t_id
inner join score as s on s.c_id=c.c_id
where t_name=’张三’)
8、查询没学过"张三"老师授课的同学的信息
Select*
From student
Where s_id not in(
select s.s_id from teacher as t
inner join course as c on t.t_id=c.t_id
inner join score as s on s.c_id=c.c_id
where t_name=’张三’)
9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息
Select*
From student
Where s_id in(select c_id from score where c_id=’01’ and c_id=’02’)
10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息
Select*
From student
Where s_id in(select s_id from score where c_id=’01’ and c_id!=’02’)
11、查询没有学全所有课程的同学的信息
Select*
From student
Where s_id in(select s_id from score where c_id is null or c_id=’’)
12、查询至少有一门课与学号为"01"的同学所学相同的同学的信息
Select*
From student as s
Inner join score as sc on s.s_id-sc.s_id
Where sc.c_id in (select c_id from score where s_id=’01’)
13、查询和"01"号的同学学习的课程完全相同的其他同学的信息
Select*
From student as s
Inner join score as sc on s.s_id-sc.s_id
Where sc.c_id = (select c_id from score where s_id=’01’)
14、查询没学过"张三"老师讲授的任一门课程的学生姓名
Select s_name as 学生姓名
From student
Where s_id not in(select s_id from score where c_id in（select c_id from course where t_id in（select t_id from teacher where t_name=’张三’）)）
15、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩
Select s.s_id as 学生学号，s.s_name as 学生姓名，avg（sc.s_score）as 平均成绩
From student as s
Inner join score as sc on s.s_id=sc.s_id
Where s.s_id in(select s_id from score where s_score<60 group by s_id having count(s_id)>2)
Group by s.s_id,s.s_name