表的一些基本操作
1.导入sql文件
source + 文件位置
2.查询某列的数据
select col1, col2, col3 from table
3.查询所有数据
select * from table
4.查询Score表中成绩在60到80之间的所有记录
select Degree from Score where Degree >= 60 and Degree <=80;
5.查询Score表中成绩为68,86的记录
select Degree from Score where Degree = 68 or Degree =86;
6.查询Student表中“9001”班或性别为“女”的同学记录
select * from Student where Class = '9001' or Ssex = '女';
7.排序查询
7.1 降序关键字desc,以Class降序查询Student表的所有记录
select * from Student order by Class desc;
7.2 升序:order by + colname,以Cno升序、Degree降序查询Score表的所有记录
select * from Student order by Cno, Degree desc;
8.查询student表中“9002”班的学生人数
select count(Class) as '9002' from Student;
9.查询Score表中的最高分和最低分
select max(Degree), min(Degree) from Score;
10.查询Score表每门课的平均成绩
select Sno, avg(Degree) from Score group by Sno;
11.查询Score表中至少有3名学生选修的,并且课程号以02结尾的课程的平均分数
select Cno, avg(Degree) from Score group by Cno
having Cno like '%02' and count(*) > 3;