表的一些基本操作
1.匯入sql檔案
source + 檔案位置
2.查詢某列的資料
select col1, col2, col3 from table
3.查詢所有資料
select * from table
4.查詢Score表中成績在60到80之間的所有記錄
select Degree from Score where Degree >= 60 and Degree <=80;
5.查詢Score表中成績為68，86的記錄
select Degree from Score where Degree = 68 or Degree =86;
6.查詢Student表中“9001”班或性別為“女”的同學記錄
select * from Student where Class = '9001' or Ssex = '女';
7.排序查詢
7.1 降序關鍵字desc，以Class降序查詢Student表的所有記錄
select * from Student order by Class desc;
7.2 升序：order by + colname，以Cno升序、Degree降序查詢Score表的所有記錄
select * from Student order by Cno, Degree desc;
8.查詢student表中“9002”班的學生人數
select count(Class) as '9002' from Student;
9.查詢Score表中的最高分和最低分
select max(Degree), min(Degree) from Score;
10.查詢Score表每門課的平均成績
select Sno, avg(Degree) from Score group by Sno;
11.查詢Score表中至少有3名學生選修的，並且課程號以02結尾的課程的平均分數
select Cno, avg(Degree) from Score group by Cno
having Cno like '%02' and count(*) > 3;