MySQL数据库-----视图的的相关操作

1 案例1：视图的基本使用

1.1 问题
• 把/etc/passwd文件的内容存储到db9库下的user表里
• 添加新字段id 存储记录的行号(在所有字段的前边)
• 创建视图v1 结构及数据user表的字段、记录一样。
• 创建视图v2 只有user表shell是/bin/bash用户信息 。
• 分别对视图表和基表执行insert update delete 操作。
• 删除视图v1 和 v2

1.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：视图的基本使用
什么是视图：是一种虚拟存在的表
内容与真实的表相似，包含一系列带有名称的列和行数据。
视图并不在数据库中以存储的数据的形式存在。
行和列的数据来自定义视图时查询所引用的基本表，并且在具体引用视图时动态生成。
更新视图的数据，就是更新基表的数据
更新基表数据，视图的数据也会跟着改变
1）把/etc/passwd文件的内容存储到db9库下的user表里

1.	[root@zlz ~]  # mysql -u root -p123456
2.	mysql> create database db9;
3.	Query OK, 1 row affected (10.00 sec)
4.	mysql> create table db9.user(username char(20),password char(1),uid \ 
5.	int(2),gid int(2),comment char(100),homedir char(100),shell char(50));
6.	//创建存储数据的表结构
7.	Query OK, 0 rows affected (0.02 sec)
8.	[root@zlz ~]  #  cp /etc/passwd /var/lib/mysql-files/
9.	[root@zlz ~]  # ls /var/lib/mysql-files/
10.	passwd
11.	mysql>  load data infile "/var/lib/mysql-files/passwd"  into table db9.user fields terminated by ":"  lines terminated by "\n";        //导入文件内容到db9.user
12.	Query OK, 41 rows affected (0.02 sec)
13.	Records: 41  Deleted: 0  Skipped: 0  Warnings: 0

2）添加新字段id 存储记录的行号(在所有字段的前边)

1.	mysql>  alter table db9.user add id int(2) primary key auto_increment first;
2.	Query OK, 0 rows affected (0.04 sec)
3.	Records: 0  Duplicates: 0  Warnings: 0
4.	mysql> use db9;
5.	mysql> desc user;
6.	+----------+-----------+------+-----+---------+----------------+
7.	| Field    | Type      | Null | Key | Default | Extra          |
8.	+----------+-----------+------+-----+---------+----------------+
9.	| id       | int(2)    | NO   | PRI | NULL    | auto_increment |
10.	| username | char(20)  | YES  |     | NULL    |                |
11.	| password | char(1)   | YES  |     | NULL    |                |
12.	| uid      | int(2)    | YES  |     | NULL    |                |
13.	| gid      | int(2)    | YES  |     | NULL    |                |
14.	| comment  | char(100) | YES  |     | NULL    |                |
15.	| homedir  | char(100) | YES  |     | NULL    |                |
16.	| shell    | char(50)  | YES  |     | NULL    |                |
17.	+----------+-----------+------+-----+---------+----------------+
18.	8 rows in set (0.00 sec)

3）创建视图v1 结构及数据user表的字段、记录一样

1.	mysql> create view v1 as select * from user;
2.	Query OK, 0 rows affected (0.00 sec)

4）创建视图v2 只有user表shell是/bin/bash用户信息

1.	mysql>  create view v2 as select shell from user;
2.	Query OK, 0 rows affected (0.01 sec)

5）分别对视图表和基表执行insert update delete 操作

1.	mysql>  insert into v1(username,uid) values("jarry",9);        //插入记录
2.	Query OK, 1 row affected (0.00 sec)
3.	
4.	mysql>  update v1 set uid=9 where username="adm";        //更新记录
5.	Query OK, 1 row affected (0.01 sec)
6.	Rows matched: 1  Changed: 1  Warnings: 0
7.	
8.	mysql> delete from v1 where uid=9;            //删除记录
9.	Query OK, 2 rows affected (0.01 sec)

6）删除视图v1 和 v2

1.	mysql> drop view v1;
2.	Query OK, 0 rows affected (0.00 sec)
3.	mysql> drop view v2;
4.	Query OK, 0 rows affected (0.00 sec)

注意：对视图操作即是对基本操作，反之亦然！！！

2 案例2：视图进阶操作

2.1 问题
• 练习OR REPLACE的选项使用
• 练习WITH LOCAL CHECK OPTION 选项的使用
• 练习WITH CASCADED CHECK OPTION 选项的使用
2.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：视图进阶操作
1）创建视图完全格式

1.	mysql>  create table user2 select  username,uid,gid from user  limit 3;
2.	//快速建表（user2表）
3.	Query OK, 3 rows affected (0.01 sec)
4.	Records: 3  Duplicates: 0  Warnings: 0
5.	
6.	mysql> create table info select  username,uid,homedir,shell from user  limit 5;
7.	//快速建表（info表）
8.	Query OK, 5 rows affected (0.02 sec)
9.	Records: 5  Duplicates: 0  Warnings: 0

查询user2.username=info.username的字段

1.	mysql> select * from user2  left join info on  user2.username=info.username;
2.	+----------+------+------+----------+------+---------+---------------+
3.	| username | uid  | gid  | username | uid  | homedir | shell         |
4.	+----------+------+------+----------+------+---------+---------------+
5.	| root     |    0 |    0 | root     |    0 | /root   | /bin/bash     |
6.	| bin      |    1 |    1 | bin      |    1 | /bin    | /sbin/nologin |
7.	| daemon   |    2 |    2 | daemon   |    2 | /sbin   | /sbin/nologin |
8.	+----------+------+------+----------+------+---------+---------------+
9.	3 rows in set (0.00 sec)

2）关联查询建的视图 默认不允许修改视图字段的值

1.	mysql>  create view v4 as select * from user2  left join info on  user2.username=info.username;        //创建失败
2.	ERROR 1060 (42S21): Duplicate column name 'username'
3.	
4.	mysql>  create view v4 as select a.username as ausername,b.username as busername,  a.uid as auid,b.uid as buid  from user2 a  left join info b  on  a.username=b.username;
5.	//创建成功
6.	Query OK, 0 rows affected (0.00 sec)
7.	
8.	mysql> select * from v4;        
9.	+-----------+-----------+------+------+
10.	| ausername | busername | auid | buid |
11.	+-----------+-----------+------+------+
12.	| root      | root      |    0 |    0 |
13.	| bin       | bin       |    1 |    1 |
14.	| daemon    | daemon    |    2 |    2 |
15.	+-----------+-----------+------+------+
16.	3 rows in set (0.00 sec)
17.	
18.	mysql> desc v4;
19.	+-----------+----------+------+-----+---------+-------+
20.	| Field     | Type     | Null | Key | Default | Extra |
21.	+-----------+----------+------+-----+---------+-------+
22.	| ausername | char(20) | YES  |     | NULL    |       |
23.	| busername | char(20) | YES  |     | NULL    |       |
24.	| auid      | int(2)   | YES  |     | NULL    |       |
25.	| buid      | int(2)   | YES  |     | NULL    |       |
26.	+-----------+----------+------+-----+---------+-------+
27.	4 rows in set (0.00 sec)

3）OR REPLACE的选项使用
创建时，若视图已存在，会替换已有的视图
语法格式：create or replace view视图名as select 查询； //达到修改已有视图的目的

1.	mysql> create  or  replace view v4 as select a.username as ausername,b.username as busername,  a.uid as auid,b.uid as buid  from user2 a  left join info b  on  a.username=b.username;
2.	Query OK, 0 rows affected (0.00 sec)

4）WITH LOCAL CHECK OPTION
LOCAL和CASCADED关键字决定检查的范围
LOCAL 仅检查当前视图的限制
CASCADED 同时要满足基表的限制（默认值）

1.	mysql> create table user1  select username,uid,shell from user where uid>=5 and uid <=40;  
2.	Query OK, 11 rows affected (0.01 sec)
3.	Records: 11  Duplicates: 0  Warnings: 0
4.	
5.	mysql> create view v1 as select username,uid from user1 where uid<=20;
6.	Query OK, 0 rows affected (0.01 sec)
7.	
8.	mysql> update v1 set uid=21 where  username="sync";     
9.	//操作超过视图表的条件限制（uid<=20）之后，在视图表里面查看不到，在基表里可以查看到
10.	Query OK, 1 row affected (0.01 sec)
11.	Rows matched: 1  Changed: 1  Warnings: 0
12.	
13.	mysql> update user1 set uid=41 where  username="ftp";
14.	//基表在超过条件限制（uid>=5 and uid <=40),在基表里依然可以查看到
15.	Query OK, 1 row affected (0.00 sec)
16.	Rows matched: 1  Changed: 1  Warnings: 0
17.	
18.	mysql>  create table a select * from user where uid < 10;
19.	//快速创建一个新表a
20.	Query OK, 7 rows affected (0.01 sec)
21.	Records: 7  Duplicates: 0  Warnings: 0
22.	
23.	mysql> create view v3 as select * from a where uid < 10 with  check option;
24.	//不写默认为CASCADED检查自己和a要满足的要求即可
25.	Query OK, 0 rows affected (0.00 sec)
26.	
27.	mysql> update v3 set uid=9 where username="adm";    //更改成功
28.	Query OK, 0 rows affected (0.01 sec)
29.	Rows matched: 0  Changed: 0  Warnings: 0
30.	
31.	
32.	mysql> create view v2 as select * from v1 where uid >= 5 with local check option;
33.	//满足自身v2的要求
34.	Query OK, 0 rows affected (0.00 sec)
35.	mysql>  update v2 set uid=9 where username="sync";
36.	Query OK, 0 rows affected (0.00 sec)
37.	Rows matched: 0  Changed: 0  Warnings: 0

5）WITH CASCADED CHECK OPTION

1.	mysql>  create view v5 as select * from v1 where uid >= 5 with cascaded check option;
2.	Query OK, 0 rows affected (0.00 sec)

3 案例3：创建存储过程

3.1 问题
• 存储过程名称为p1
• 功能显示user表中 shell是/bin/bash的用户个数
• 调用存储过程p1
3.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：存储过程基本使用
1）创建存储过程

1.	mysql> delimiter  //          //定义定界符
2.	mysql>  create procedure say()     //say()随便写括号一定要有
3.	    -> begin
4.	    -> select * from user where id<=10;
5.	    -> end
6.	    -> //
7.	Query OK, 0 rows affected (0.01 sec)
8.	mysql> delimiter ;        //把命令的定界符改回来，分号前有空格
9.	mysql> call say();    //调用存储过程名,在括号里面不写参数时，可以不加括号

2）查看存储过程
方法一：

1.	mysql>  show  procedure  status\G;

方法二：

1.	mysql>  select db,name,type from mysql.proc where name= "say";

3）删除存储过程

1.	mysql> drop procedure say;
2.	Query OK, 0 rows affected (0.00 sec)

4）Ÿ创建存储过程名称为p1
Ÿ 功能显示user表中 shell是/bin/bash的用户
Ÿ 调用存储过程p1

1.	mysql> delimiter  //
2.	mysql> create procedure p1()
3.	    -> begin
4.	    -> select count(username)  from user where shell="/bin/bash";
5.	    -> end
6.	    -> //
7.	mysql> delimiter ;
8.	mysql> call p1();
9.	+-----------+
10.	| shell     |
11.	+-----------+
12.	| /bin/bash |
13.	| /bin/bash |
14.	+-----------+
15.	2 rows in set (0.01 sec)
16.	
17.	Query OK, 0 rows affected (0.01 sec)

4 案例4：存储过程参数的使用

4.1 问题
• 创建名为p2的存储过程
• 可以接收用户输入shell的名字
• 统计user表中用户输入shell名字的个数
4.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：存储过程参数的使用
1）参数类型
MySQL存储过程，共有三种参数类型IN,OUT,INOUT
Create procedure 名称(
类型 参数名 数据类型,
类型 参数名 数据类型
）
in 输入参数 传递值给存储过程，必须在调用存储过程时指定，在存储过程中修改该参数的值不能；默认类型是in
out 输出参数 该值可在存储过程内部被改变，并可返回
inout 输入/输出参数 调用时指定，并且可被改变和返回

1.	mysql>  delimiter  //
2.	mysql>  create procedure say2(in username char(10))
3.	    -> begin
4.	    -> select username;
5.	    -> select * from user where username=username;
6.	    -> end
7.	    -> //
8.	Query OK, 0 rows affected (0.00 sec)
9.	
10.	mysql> delimiter ;
11.	mysql> call say2("tom");

2）创建名为p2的存储过程，可以接收用户输入shell的名字，统计user表中用户输入shell名字的个数

1.	mysql>  delimiter  //
2.	mysql>  create procedure p2(out number int)
3.	    -> begin
4.	    -> select count(username) into @number from user where shell!="/bin/bash"; 
5.	    -> select @number;
6.	    -> end
7.	    -> //
8.	Query OK, 0 rows affected (0.01 sec)
9.	mysql> delimiter ;
10.	mysql> call p2(@number);
11.	+---------+
12.	| @number |
13.	+---------+
14.	|      38 |
15.	+---------+
16.	1 row in set (0.00 sec)
17.	
18.	Query OK, 0 rows affected (0.00 sec)

5 案例5：使用循环结构

5.1 问题
• 定义名称为p3的存储过程
• 用户可以自定义显示user表记录的行数
• 若调用时用户没有输入行数，默认显示第1条记录
5.2 步骤
实现此案例需要按照如下步骤进行。
步骤一：算数运算
1）算 数运算符号，如图-1所示：

图-1

1.	mysql> set @z=1+2;select @z;
2.	Query OK, 0 rows affected (0.00 sec)
3.	
4.	+------+
5.	| @z   |
6.	+------+
7.	|    3 |
8.	+------+
9.	1 row in set (0.00 sec)
10.	mysql> set @x=1; set @y=2;set @z=@x*@y; select @z;
11.	Query OK, 0 rows affected (0.00 sec)
12.	
13.	Query OK, 0 rows affected (0.00 sec)
14.	
15.	Query OK, 0 rows affected (0.00 sec)
16.	
17.	+------+
18.	| @z   |
19.	+------+
20.	|    2 |
21.	+------+
22.	1 row in set (0.00 sec)
23.	
24.	mysql> set @x=1; set @y=2;set @z=@x-@y; select @z;
25.	Query OK, 0 rows affected (0.00 sec)
26.	
27.	Query OK, 0 rows affected (0.00 sec)
28.	
29.	Query OK, 0 rows affected (0.00 sec)
30.	
31.	+------+
32.	| @z   |
33.	+------+
34.	|   -1 |
35.	+------+
36.	1 row in set (0.00 sec)
37.	mysql> set @x=1; set @y=2;set @z=@x/@y; select @z;
38.	Query OK, 0 rows affected (0.00 sec)
39.	
40.	Query OK, 0 rows affected (0.00 sec)
41.	
42.	Query OK, 0 rows affected (0.00 sec)
43.	
44.	+-------------+
45.	| @z           |
46.	+-------------+
47.	| 0.500000000 |
48.	+-------------+
49.	1 row in set (0.00 sec)

declare调用变量不需要@其他都需要
调用变量时，有@符号的变量 如@x：调用的是用户自定义变量
没有@符号的变量 如x：调用的是存储过程的参数变量

1.	mysql> delimiter //
2.	mysql> create procedure say5(in bash char(20), in  nologin char(25), out x int , out y int)
3.	    -> begin
4.	    -> declare z int ;
5.	    -> set z=0;
6.	    -> select count(username) into  @x from user where shell=bash;
7.	    -> select count(username) into  @y from user where shell=nologin;
8.	    -> set z=@x+@y;
9.	    -> select z;
10.	    -> end
11.	    ->  //
12.	Query OK, 0 rows affected (0.00 sec)
13.	
14.	mysql> delimiter ;
15.	mysql>  call say5("/bin/bash","/sbin/nologin",@x,@y);
16.	+------+
17.	| z    |
18.	+------+
19.	|   36 |
20.	+------+
21.	1 row in set (0.00 sec)
22.	
23.	Query OK, 0 rows affected (0.00 sec)

2）条件判断，数值的比较 如图-2所示：

图-2
逻辑比较、范围、空、非空、模糊、正则，如图-3所示：

图-3
顺序结构（if判断）当“条件成立”时执行命令序列,否则，不执行任何操作

1.	mysql> delimiter //
2.	mysql>  create  procedure say6(in  x int(1) )
3.	    -> begin
4.	    ->  if x <= 10 then
5.	    ->  select * from user where id <=x;
6.	    -> end if;
7.	    -> end
8.	    -> //
9.	Query OK, 0 rows affected (0.01 sec)
10.	
11.	mysql> delimiter ;
12.	mysql> call say6(1);        //条件判断成立，等于1是否成立
13.	+----+----------+----------+------+------+---------+---------+-----------+
14.	| id | username | password | uid  | gid  | comment | homedir | shell     |
15.	+----+----------+----------+------+------+---------+---------+-----------+
16.	|  1 | root     | x        |    0 |    0 | root    | /root   | /bin/bash |
17.	+----+----------+----------+------+------+---------+---------+-----------+
18.	1 row in set (0.00 sec)
19.	
20.	Query OK, 0 rows affected (0.00 sec)
21.	
22.	mysql> call say6(2);
23.	+----+----------+----------+------+------+---------+---------+---------------+
24.	| id | username | password | uid  | gid  | comment | homedir | shell         |
25.	+----+----------+----------+------+------+---------+---------+---------------+
26.	|  1 | root     | x        |    0 |    0 | root    | /root   | /bin/bash     |
27.	|  2 | bin      | x        |    1 |    1 | bin     | /bin    | /sbin/nologin |
28.	+----+----------+----------+------+------+---------+---------+---------------+
29.	2 rows in set (0.00 sec)
30.	
31.	Query OK, 0 rows affected (0.00 sec)

3）定义名称为p3的存储过程，用户可以自定义显示user表记录的行数，若调用时用户没有输入行数，默认显示第1条记录

1.	mysql> delimiter //
2.	mysql> create  procedure p3(in  linenum char(10) )
3.	    -> begin
4.	    -> if linenum is null then
5.	    -> set @linenum=1;
6.	    -> select * from user where id=@linenum;
7.	    -> else
8.	    -> select linenum;
9.	    -> select * from user where id=linenum;
10.	    -> end if;
11.	    -> end
12.	    -> //
13.	Query OK, 0 rows affected (0.00 sec)
14.	
15.	mysql> delimiter ;
16.	mysql> call p3(null);        //不输入查看的行数
17.	+----+----------+----------+------+------+---------+---------+-----------+
18.	| id | username | password | uid  | gid  | comment | homedir | shell     |
19.	+----+----------+----------+------+------+---------+---------+-----------+
20.	|  1 | root     | x        |    0 |    0 | root    | /root   | /bin/bash |
21.	+----+----------+----------+------+------+---------+---------+-----------+
22.	1 row in set (0.00 sec)
23.	
24.	Query OK, 0 rows affected (0.00 sec)
25.	
26.	mysql> call p3(3);        //输入查看的行数
27.	+---------+
28.	| linenum |
29.	+---------+
30.	| 3       |
31.	+---------+
32.	1 row in set (0.00 sec)
33.	
34.	+----+----------+----------+------+------+---------+---------+---------------+
35.	| id | username | password | uid  | gid  | comment | homedir | shell         |
36.	+----+----------+----------+------+------+---------+---------+---------------+
37.	|  3 | daemon   | x        |    2 |    2 | daemon  | /sbin   | /sbin/nologin |
38.	+----+----------+----------+------+------+---------+---------+---------------+
39.	1 row in set (0.00 sec)
40.	
41.	Query OK, 0 rows affected (0.00 sec)