1.作业
1.查询全部课程的信息。
SELECT * FROM course;
2.查询信工学院开设的课程名、课程号及学分。
SELECT cs_name,cs_id,cs_credit
FROM course
WHERE cs_depart ="信工";
3.查询学分超过3学分的课程代码、课程名和开课单位。
SELECT cs_id AS " 课程代码",cs_name AS " 课程名",cs_type AS " 开课单位"
FROM course
WHERE cs_credit>=3;
4.查询计科专业和大数据专业的学生信息。
SELECT *
FROM student
WHERE stu_major="计科"||stu_major="大数据;
5.查询不是信工学院的学生姓名和学号。
select * from student where stu_college != "信工学院";
6.查询年龄是17,18,19的学生姓名和专业。
SELECT stu_name,stu_major
FROM student
WHERE stu_age in (17,18,19);
7.查询学分在2到4之间课程的信息。
SELECT *
FROM course
WHERE cs_credit BETWEEN 2 AND 4;
8.查询课程名称中带“数据”的课程名、课程号及开课单位。
select cs_name as '课程名',cs_id as '课程号',cs_depart as '开课单位'
from course
where cs_name like '%数据%';
9.查询信工学院的的专业有哪些。
select distinct stu_major as '专业',stu_college as '学院名'
from student
where stu_college = '信工学院';
10.查询年龄为空的学生信息。
select * from student where stu_age is null;
11.查询不是信工学院开设的集中实践课的开课单位和课程名称。
select cs_depart as '开课单位',cs_name as '课程名称'
from course
where cs_depart != '信工' and cs_type = '集中实践';
12.查询信工学院开设的课程的类型有哪些。
#distinct 不重复统计
select distinct cs_type as '课程类型',cs_depart as '学院名'
from course
where cs_depart = '信工';
13.查询学生所在的专业个数。
select stu_major as '专业',count(stu_id) as '个数'
from student
group by stu_major;
14.查询信工学院开设的课程的平均学分。
select avg(cs_credit) from course where cs_depart = "信工";
15.查询学生的信息，查询结果按姓名升序排序。
select *
from student
order by stu_name;
16.查询 每个专业的学生的最大年龄、最小年龄和平均年龄，查询结果按平均年龄降序排列。
select stu_major as '专业',max(stu_age) as '最大年龄',min(stu_age) as '最小年龄',avg(stu_age) as '平均年龄'
from student
group by stu_major
order by 平均年龄 desc;
17.查询每个开课单位开设的课程门数的数量，直询结果按课程门数升序排列。
SELECT cs_depart, COUNT(cs_name)
FROM course
GROUP BY cs_depart ORDER BY COUNT(cs_name);
18.查询单位开课门数少于2门的开课单位和课程名称。
SELECT cs_depart,cs_name
FROM course
GROUP BY cs_depart having COUNT(cs_name)<2;
