使用SQL语句对表的操作

学生表：Student (Sno, Sname, Ssex , Sage, Sdept)

学号，姓名，性别，年龄，所在系 Sno为主键

课程表：Course (Cno, Cname)

课程号，课程名 Cno为主键

学生选课表：SC (Sno, Cno, Score)

学号，课程号，成绩 Sno,Cno为主键

1. 用SQL语句创建学生表student，定义主键，姓名不能重名，性别只能输入男或女，所在系的默认值是 “计算机”。

mysql8.0 [chap03]>create table stydent(
    -> son int primary key,
    -> sname char(30) unique,
    -> ssex char(1) check (ssex in ('F','M')),
    -> sage int,
    -> sdept char(20) default 'IT'
    -> );
Query OK, 0 rows affected (0.03 sec)
mysql8.0 [chap03]>desc student;

2. 修改student 表中年龄（age）字段属性，数据类型由int 改变为smallint。

mysql8.0 [chap03]>alter table student modify sage smallint;
Query OK, 0 rows affected (0.03 sec)
Records: 0  Duplicates: 0  Warnings: 0

3. 为SC表建立按学号（sno）和课程号（cno）组合的升序的主键索引，索引名为SC_INDEX 。

mysql8.0 [chap03]>create index sc_index on sc (sno asc,cno asc);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql8.0 [chap03]>show index from sc;

4. 创建一视图 stu_info,查询全体学生的姓名，性别，课程名，成绩。

mysql8.0 [chap03]>insert into student values (1,'xiaoming','M',18,'english'),(2,'xiaohong','F',19,'chinese'),(3,'xiaolan','F',17,'IT');
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql8.0 [chap03]>select * from student;

mysql8.0 [chap03]>insert into course values (1,'music'),(2,'history'),(3,'PE');
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql8.0 [chap03]>select * from course;

mysql8.0 [chap03]>insert into sc values (1,2,80),(1,3,15),(2,1,10),(2,2,59);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql8.0 [chap03]>create view stu_info as select st.sname,st.ssex,co.cname,sc.sc
ore from student st,course co,sc where st.son=sc.sno and co.cno=sc.cno;
Query OK, 0 rows affected (0.01 sec)

mysql8.0 [chap03]>select * from stu_info;