案例1：创建存储过程
案例2：存储过程参数的使用
案例3：使用循环结构
1 案例1：创建存储过程
1.1 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
1.2 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
mysql> delimiter // //定义定界符
mysql> create procedure say() //say()随便写括号一定要有
-> begin
-> select * from user where id<=10;
-> end
-> //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ; //把命令的定界符改回来，分号前有空格
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：
mysql> show procedure status\G;
方法二：
mysql> select db,name,type from mysql.proc where name= "say";
3）删除存储过程
mysql> drop procedure say;
Query OK, 0 rows affected (0.00 sec)
4）创建存储过程名称为p1
功能显示user表中 shell是/bin/bash的用户
调用存储过程p1
mysql> delimiter //
mysql> create procedure p1()
-> begin
-> select count(username) from user where shell="/bin/bash";
-> end
-> //
mysql> delimiter ;
mysql> call p1();
+-----------+
| shell |
+-----------+
| /bin/bash |
| /bin/bash |
+-----------+
2 rows in set (0.01 sec)
Query OK, 0 rows affected (0.01 sec)
2 案例2：存储过程参数的使用
2.1 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
2.2 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
mysql> delimiter //
mysql> create procedure say2(in username char(10))
-> begin
-> select username;
-> select * from user where username=username;
-> end
-> //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
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
mysql> delimiter //
mysql> create procedure p2(out number int)
-> begin
-> select count(username) into @number from user where shell!="/bin/bash";
-> select @number;
-> end
-> //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;
mysql> call p2(@number);
+---------+
| @number |
+---------+
| 38 |
+---------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
3 案例3：使用循环结构
3.1 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
3.2 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
mysql> set @z=1+2;select @z;
Query OK, 0 rows affected (0.00 sec)
+------+
| @z |
+------+
| 3 |
+------+
1 row in set (0.00 sec)
mysql> set @x=1; set @y=2;set @z=@x*@y; select @z;
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
+------+
| @z |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
mysql> set @x=1; set @y=2;set @z=@x-@y; select @z;
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
+------+
| @z |
+------+
| -1 |
+------+
1 row in set (0.00 sec)
mysql> set @x=1; set @y=2;set @z=@x/@y; select @z;
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
+-------------+
| @z |
+-------------+
| 0.500000000 |
+-------------+
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
mysql> delimiter //
mysql> create procedure say5(in bash char(20), in nologin char(25), out x int , out y int)
-> begin
-> declare z int ;
-> set z=0;
-> select count(username) into @x from user where shell=bash;
-> select count(username) into @y from user where shell=nologin;
-> set z=@x+@y;
-> select z;
-> end
-> //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql> call say5("/bin/bash","/sbin/nologin",@x,@y);
+------+
| z |
+------+
| 36 |
+------+
1 row in set (0.00 sec)
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
mysql> delimiter //
mysql> create procedure say6(in x int(1) )
-> begin
-> if x <= 10 then
-> select * from user where id <=x;
-> end if;
-> end
-> //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;
mysql> call say6(1); //条件判断成立，等于1是否成立
+----+----------+----------+------+------+---------+---------+-----------+
| id | username | password | uid | gid | comment | homedir | shell |
+----+----------+----------+------+------+---------+---------+-----------+
| 1 | root | x | 0 | 0 | root | /root | /bin/bash |
+----+----------+----------+------+------+---------+---------+-----------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> call say6(2);
+----+----------+----------+------+------+---------+---------+---------------+
| id | username | password | uid | gid | comment | homedir | shell |
+----+----------+----------+------+------+---------+---------+---------------+
| 1 | root | x | 0 | 0 | root | /root | /bin/bash |
| 2 | bin | x | 1 | 1 | bin | /bin | /sbin/nologin |
+----+----------+----------+------+------+---------+---------+---------------+
2 rows in set (0.00 sec)
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
mysql> delimiter //
mysql> create procedure p3(in linenum char(10) )
-> begin
-> if linenum is null then
-> set @linenum=1;
-> select * from user where id=@linenum;
-> else
-> select linenum;
-> select * from user where id=linenum;
-> end if;
-> end
-> //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql> call p3(null); //不输入查看的行数
+----+----------+----------+------+------+---------+---------+-----------+
| id | username | password | uid | gid | comment | homedir | shell |
+----+----------+----------+------+------+---------+---------+-----------+
| 1 | root | x | 0 | 0 | root | /root | /bin/bash |
+----+----------+----------+------+------+---------+---------+-----------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> call p3(3); //输入查看的行数
+---------+
| linenum |
+---------+
| 3 |
+---------+
1 row in set (0.00 sec)
+----+----------+----------+------+------+---------+---------+---------------+
| id | username | password | uid | gid | comment | homedir | shell |
+----+----------+----------+------+------+---------+---------+---------------+
| 3 | daemon | x | 2 | 2 | daemon | /sbin | /sbin/nologin |
+----+----------+----------+------+------+---------+---------+---------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
