新建数据库

mysql> create database mydb15_indexstu;
Query OK, 1 row affected (0.00 sec)

mysql>  use mydb15_indexstu;
Database changed

新建表

建立student表
mysql> create table student(Sno int primary key auto_increment,
    -> Sname varchar(30) not null unique,
    -> Ssex varchar(2) check(Ssex='男' or Ssex='女') not null,
    -> Sage int not null,
    -> Sdept varchar(10) default '计算机' not null);
Query OK, 0 rows affected (0.02 sec)


建立SC表
mysql> create table SC(Sno int not null,
    ->  Cno varchar(10) primary key not null,
    -> Score int not null);
Query OK, 0 rows affected (0.01 sec)



建立Course表
mysql> create table Course(Cno int primary key not null,
    -> Cname varchar(20) not null);
Query OK, 0 rows affected (0.01 sec)

处理表

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

mysql> desc student;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| Sno   | int         | NO   | PRI | NULL    | auto_increment |
| Sname | varchar(30) | NO   | UNI | NULL    |                |
| Ssex  | varchar(2)  | NO   |     | NULL    |                |
| Sage  | int         | NO   |     | NULL    |                |
| Sdept | varchar(10) | NO   |     | 计算机  |                |
+-------+-------------+------+-----+---------+----------------+
5 rows in set (0.01 sec)

mysql> alter table student modify Sage smallint;
Query OK, 0 rows affected (0.03 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc student;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| Sno   | int         | NO   | PRI | NULL    | auto_increment |
| Sname | varchar(30) | NO   | UNI | NULL    |                |
| Ssex  | varchar(2)  | NO   |     | NULL    |                |
| Sage  | smallint    | YES  |     | NULL    |                |
| Sdept | varchar(10) | NO   |     | 计算机  |                |
+-------+-------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

2.为Course表中Cno 课程号字段设置索引,并查看索引

mysql> create index index_con on Course(Cno);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show index from Course;
+--------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table  | Non_unique | Key_name  | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
+--------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| course |          0 | PRIMARY   |            1 | Cno         | A         |           0 |     NULL |   NULL |      | BTREE      |         |
   | YES     | NULL       |
| course |          1 | index_con |            1 | Cno         | A         |           0 |     NULL |   NULL |      | BTREE      |         |
   | YES     | NULL       |
+--------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
2 rows in set (0.00 sec)

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

mysql> desc SC;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| Sno   | int         | NO   |     | NULL    |       |
| Cno   | varchar(10) | NO   | PRI | NULL    |       |
| Score | int         | NO   |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> alter table SC drop primary key;
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> alter table SC add primary key(Sno,Cno);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc SC;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| Sno   | int         | NO   | PRI | NULL    |       |
| Cno   | varchar(10) | NO   | PRI | NULL    |       |
| Score | int         | NO   |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

4.创建一视图 stu info,查询全体学生的姓名，性别，课程名，成绩

mysql> create view stu_info as select student.Sname,student.Ssex,Course.Cname,SC.Score
    -> from student,SC,Course where student.Sno=SC.Sno and SC.Cno=Course.Cno;
Query OK, 0 rows affected (0.00 sec)

mysql> desc stu_info;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| Sname | varchar(30) | NO   |     | NULL    |       |
| Ssex  | varchar(2)  | NO   |     | NULL    |       |
| Cname | varchar(20) | NO   |     | NULL    |       |
| Score | int         | NO   |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

5.删除所有索引

mysql> drop index index_cno on Course;

mysql> drop index SC_INDEX on SC;