Mysql作业4

lcanfly2025-11-08 14:23

新建数据库

复制代码 
mysql> create database mydb15_indexstu;
Query OK, 1 row affected (0.01 sec)

mysql> use mydb15_indexstu;
Database changed

新建表

1、学生表student，定义主键，姓名不能重名，性别只能输入勇或女，所在系的默认值是"计算机"，结构如下Student(Sno学号，Sname 姓名，Ssex 性别，Sage 年龄，sdept 所在系)Sno为主键

复制代码 
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)

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 (0.00 sec)

2、用SQL语句创建课程表：Course(Cno课程号，Cname课程名)Cno为主键

复制代码 
mysql> create table Sc(
    -> Sno int not null,
    -> Cno varchar(10) primary key not null,
    -> Score int not null );
Query OK, 0 rows affected (0.02 sec)

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)

3.用SQL语句创建选课表：sc(Sno学号，Cno 课程号，score成绩)Sno,Cno为主键

复制代码 
mysql> create table Course (
    -> Cno int priarmy key not null,
    -> Cname varchar(20) not null ) ;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'priarmy key not null,
Cname varchar(20) not null )' at line 2
mysql> create table Course ( Cno int primary key not null, Cname varchar(20) not null );
Query OK, 0 rows affected (0.01 sec)

mysql> desc  Course;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| Cno   | int         | NO   | PRI | NULL    |       |
| Cname | varchar(20) | NO   |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 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

复制代码 
mysql>
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

复制代码 
mysql> desc Course;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| Cno   | int         | NO   | PRI | NULL    |       |
| Cname | varchar(20) | NO   |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> create index Course_Cno on Course(Cno);
Query OK, 0 rows affected (0.02 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 | Course_Cno |            1 | Cno         | A         |           0 |     NULL |   NULL |      | BTREE      |        |               | YES     | NULL       |
+--------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
2 rows in set (0.01 sec)

mysql> show index from  Course\G
*************************** 1. row ***************************
        Table: Course
   Non_unique: 0
     Key_name: PRIMARY
 Seq_in_index: 1
  Column_name: Cno
    Collation: A
  Cardinality: 0
     Sub_part: NULL
       Packed: NULL
         Null:
   Index_type: BTREE
      Comment:
Index_comment:
      Visible: YES
   Expression: NULL
*************************** 2. row ***************************
        Table: Course
   Non_unique: 1
     Key_name: Course_Cno
 Seq_in_index: 1
  Column_name: Cno
    Collation: A
  Cardinality: 0
     Sub_part: NULL
       Packed: NULL
         Null:
   Index_type: BTREE
      Comment:
Index_comment:
      Visible: YES
   Expression: 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

复制代码 
mysql> create unique index Sc_index on Sc(Sno asc ,Cno asc);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show index from Sc\G
*************************** 1. row ***************************
        Table: Sc
   Non_unique: 0
     Key_name: PRIMARY
 Seq_in_index: 1
  Column_name: Cno
    Collation: A
  Cardinality: 0
     Sub_part: NULL
       Packed: NULL
         Null:
   Index_type: BTREE
      Comment:
Index_comment:
      Visible: YES
   Expression: NULL
*************************** 2. row ***************************
        Table: Sc
   Non_unique: 0
     Key_name: Sc_index
 Seq_in_index: 1
  Column_name: Sno
    Collation: A
  Cardinality: 0
     Sub_part: NULL
       Packed: NULL
         Null:
   Index_type: BTREE
      Comment:
Index_comment:
      Visible: YES
   Expression: NULL
*************************** 3. row ***************************
        Table: Sc
   Non_unique: 0
     Key_name: Sc_index
 Seq_in_index: 2
  Column_name: Cno
    Collation: A
  Cardinality: 0
     Sub_part: NULL
       Packed: NULL
         Null:
   Index_type: BTREE
      Comment:
Index_comment:
      Visible: YES
   Expression: NULL
3 rows in set (0.01 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

复制代码 
mysql> select Sname '姓名' , Ssex '性别' , Cname '课程名' , Score '成绩'
    -> from Student join Sc on Student.Sno=Sc.Sno join Course on Sc.Cno=Course.Cno;
Empty set (0.00 sec)

mysql> create view stu_info as select Sname '姓名' , Ssex '性别' , Cname '课程名' , Score '成绩' from Student join Sc on Student.Sno=Sc.Sno join Course on Sc.Cno=Course.Cno;
Query OK, 0 rows affected (0.00 sec)

mysql> show tables;
+---------------------------+
| Tables_in_mydb15_indexstu |
+---------------------------+
| Course                    |
| Sc                        |
| Student                   |
| stu_info                  |
+---------------------------+
4 rows in set (0.00 sec)

5、删除所有索引

复制代码 
mysql> drop index Sc_index on Sc;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> drop index Course_Cno on Course;
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0
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