MySQL 存储过程
[toc]
存储过程概述
存储过程介绍
存储过程,相当于是 MySQL 语句组成的脚本
- 指的是数据库中保存的一系列 SQL 命令的集合
- 可以在存储过程中使用变量, 条件判断, 流程控制等
存储过程优点
- 提高性能
- 可减轻网络负担
- 可以防止对表的直接访问
- 避免重复编写 SQL 操作
基本使用
创建存储过程
语法格式
- delimiter 关键字用来指定 SQL 语句的分隔符 ( 默认为; )
- 若没有指定分割,编译器会把存储过程当成 SQL 语句进行处理,从而执行出错
delimiter //
create procedure 名称()
begin
功能代码
...
...
end
//
delimiter ;
查看存储过程
方法1
#查看 use 库中存储过程.
mysql> show procedure status;
方法2
#查看某存储过程
select db,name,type,body from mysql.proc where name="存储过程名";
调用 存储过程
#不传参时,括号可省略
call 存储过程名();
删除存储过程
drop procedure 存储过程名;
示例
#创建存储过程 say1
mysql> delimiter //
mysql> create procedure say1()
-> begin
-> select id,name,shell from db9.user;
-> select user,host from mysql.user where user="root";
-> end
-> //
mysql> delimiter ;
#调用存储过程
mysql> call say1();
#查看所有存储过程,type 是Procedure的是存储过程,Function是函数
mysql> select db,name,type from mysql.proc;
+------+-------------------------------------+-----------+
| db | name | type |
+------+-------------------------------------+-----------+
| db10 | say1 | PROCEDURE |
| sys | extract_schema_from_file_name | FUNCTION |
#查看某个存储过程
mysql> select * from mysql.proc where name="say1"\G
*************************** 1. row ***************************
db: db10
name: say1
type: PROCEDURE
specific_name: say1
language: SQL
sql_data_access: CONTAINS_SQL
is_deterministic: NO
security_type: DEFINER
param_list:
returns:
body: begin
select id,name,shell from db9.user;
select user,host from mysql.user where user="root";
end
definer: root@localhost
created: 2019-02-12 22:59:07
modified: 2019-02-12 22:59:07
sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
comment:
character_set_client: utf8
collation_connection: utf8_general_ci
db_collation: latin1_swedish_ci
body_utf8: begin
select id,name,shell from db9.user;
select user,host from mysql.user where user="root";
end
#查看存储过程 say1 具体功能
mysql> select body from mysql.proc where name="say1"\G;
*************************** 1. row ***************************
body: begin
select id,name,shell from db9.user;
select user,host from mysql.user where user="root";
end
#删除存储过程
mysql> drop procedure say1;
#创建存储过程 p1 ,功能显示user表中 shell 是 /bin/bahs的用户个数,调用p1
mysql> delimiter //
mysql> create procedure p1()
-> begin
-> select count(name) from db9.user where shell="/bin/bash";
-> end
-> //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;
mysql> call p1();
+-------------+
| count(name) |
+-------------+
| 1 |
+-------------+
1 row in set (0.00 sec)
注意
编写功能体代码时,可以使用变量 条件判断 流程控制 (if 循环) 算数计算 SQL命令
存储过程进阶
变量类型
调用局部变量时,变量名前不需要加@
| 名称 | 说明 |
|---|---|
| 会话变量 | 会话变量和全局变量叫系统变量 使用 set 命令定义 |
| 全局变量 | 全局变量的修改会影响到整个服务器,但是对会话变量的修改,只会影响当前的会话 |
| 用户变量 | 在客户端连接到数据库服务的整个过程中都是有效的.当当前连接断开后所有用户变量失效. 定义 set @变量名=值; 输出 select @变量名; |
| 局部变量 | 存储过程中的 begin end,其有效范围仅限于该语句块中,语句块执行完毕后,变量失效. declare专门用来定义局部变量 局部变量 和 参数变量 调用时,变量名前不需要加@ |
示例
#用户变量 自定义变量
mysql> set @x=20;
Query OK, 0 rows affected (0.00 sec)
mysql> select @x;
+------+
| @x |
+------+
| 20 |
#局部变量 只在存储过程中生效
mysql> delimiter //
mysql> create procedure p2()
-> begin
-> declare x int default 77;
-> declare y char(10);
-> set y="yaya";
-> select x;
-> select y;
-> end
-> //
mysql> delimiter ;
#调用存储过程
mysql> call p2;
+------+
| x |
+------+
| 77 |
+------+
1 row in set (0.00 sec)
+------+
| y |
+------+
| yaya |
+------+
1 row in set (0.00 sec)
查看变量
#查看全局变量
mysql> show global variables;
#查看会话变量
mysql> show session variables;
#设置会话变量
mysql> set seesion sort_buffer_size = 4000;
#查看会话变量
mysql> show session variables like "sort_buffer_size";
+------------------+--------+
| Variable_name | Value |
+------------------+--------+
| sort_buffer_size | 262144 |
+------------------+--------+
#查看全局变量
mysql> show global variables like "%关键字%";
#用户自定义变量 赋值
mysql>mysql> set @y=3;
mysql> select @y;
+-------+
| @y |
+-------+
| 3 |
+-------+
# 使用 SQL 查询结果 赋值
mysql> select max(uid) into @y from db9.user;
Query OK, 1 row affected (0.00 sec)
mysql> select @y;
+-------+
| @y |
+-------+
| 65534 |
+-------+
参数类型
语法格式
- 调用参数时,名称前不需要加@
create procedure 名称( 参数1, 参数2 )
- 参数格式
参数1= 类型 参数名 数据类型
create procedure p1( 类型1 参数名1 数据类型1(宽度), 类型2 参数名2 数据类型2(宽度) )
类型
| 关键字 | 名称 | 描述 |
|---|---|---|
| in | 输入型参数 (默认类型) | 作用是 给存储过程传值,必须在调用存储过程时赋值,在存储过程中该参数的值不允许修改;默认类型是in |
| out | 输出型参数 | 该值可在存储过程内部被改变,并可返回. |
| inout | 输入/输出型参数 | 调用时指定,并且可被改变和返回 |
示例
>>>>>>>>>>>>>> 输入参数 in 类型
mysql> delimiter //
#创建 in 类型 输入参数变量 username
mysql> create procedure p4(in username char(10))
-> begin
-> select username;
-> select name,shell from db9.user where name=username;
-> end
-> //
mysql> delimiter ;
#调用存储过程时赋值
mysql> call p4("mysql");
+----------+
| username |
+----------+
| mysql |
+----------+
1 row in set (0.00 sec)
+-------+------------+
| name | shell |
+-------+------------+
| mysql | /bin/false |
+-------+------------+
1 row in set (0.00 sec)
#创建p5存储过程,可以接受用户输入shell的名字,统计user表中用户输入shell名字的个数.
mysql> delimiter //
mysql> create procedure p5(in shellname char(20))
-> begin
-> select count(name),shell from db9.user where shell=shellname;
-> end
-> //
mysql> delimiter ;
mysql> call p5("/sbin/nologin");
+-------------+---------------+
| count(name) | shell |
+-------------+---------------+
| 18 | /sbin/nologin |
+-------------+---------------+
>>>>>>>>>>>>>> 输出参数 out 类型
mysql> set @x=1;
mysql> drop procedure if exists p2;
mysql> delimiter //
# 创建 out 类型 输出参数变量 num
mysql> create procedure p2(out num int(2))
-> begin
# 查看初始值
-> select num;
# 改变 num 初始值
-> set num=7;
-> select num;
# SQL查询 赋值给 num
-> select count(name) into num from db9.user where shell != "/bin/bash";
-> select num;
-> end
-> //
mysql> delimiter ;
# 调用报错 "错误的参数个数" 无论输入参数输出参数调用时都必须给出.
mysql> call p2();
ERROR 1318 (42000): Incorrect number of arguments for PROCEDURE db9.p2; expected 1, got 0
# 调用报错 "输出参数或输入输出参数不是变量" 只有输入参数可以传入常量,输出或输入输出参数都必须是变量.
mysql> call p2(22);
ERROR 1414 (42000): OUT or INOUT argument 1 for routine db9.p2 is not a variable or NEW pseudo-variable in BEFORE trigger
# 默认未将 @x 的值赋给 输出参数 变量num,只是占位所以为空.
mysql> set @x=1;
mysql> call p2(@x);
+------+
| num |
+------+
| NULL |
+------+
1 row in set (0.00 sec)
+------+
| num |
+------+
| 7 |
+------+
1 row in set (0.00 sec)
+------+
| num |
+------+
| 22 |
+------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
# 输出参数 最后会讲存储过程中的值 赋给 @x变量
mysql> select @x;
+------+
| @x |
+------+
| 22 |
+------+
>>>>>>>>>>>>>> 输入输出参数 intou类型
mysql> drop procedure if exists p3;
mysql> delimiter //
#创建p3 定义输入输出参数类型 num 变量
mysql> create procedure p3(inout num int(2))
-> begin
-> select num;
-> set num=7;
-> select num;
-> select count(name) into num from db9.user where shell != "/bin/bash";
-> select num;
-> end
-> //
mysql> delimiter ;
mysql> set @x=1;
#调用p3 传入 @x 值, @x值传给 num变量
mysql> call p3(@x);
+------+
| num |
+------+
| 1 |
+------+
1 row in set (0.00 sec)
+------+
| num |
+------+
| 7 |
+------+
1 row in set (0.00 sec)
+------+
| num |
+------+
| 22 |
+------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> select @x;
+------+
| @x |
+------+
| 22 |
+------+
1 row in set (0.00 sec)
算术运算
运算符号
| 符号 | 描述 | 示例 |
|---|---|---|
| + | 加法运算 | SET @var1=2+2; 4 |
| - | 减法运算 | SET @var2=3-2; 1 |
| * | 惩罚运算 | SET @var3=3*2; 6 |
| / | 除法运算 | SET @var4=10/3; 3.333333333 |
| DIV | 整出运算 | SET @var5=10 DIV 3; 3 |
| % | 取模 | SET @var6=10%3; 1 |
示例
#加法
mysql> SET @var1=2+2;
mysql> select @var1;
+-------+
| @var1 |
+-------+
| 4 |
+-------+
#乘法
mysql> set @i=2;
mysql> set @j=3;
mysql> set @z=@i*@j;
mysql> select @z;
+------+
| @z |
+------+
| 6 |
+------+
# 创建存储过程p6 计算 /bin/bash 和 /sbin/nologin 用户共有多少
mysql> delimiter //
mysql> create procedure p6()
-> begin
-> declare x int;
-> declare y int;
-> declare z int;
-> select count(shell) into x from db9.user where shell="/bin/bash";
-> select count(shell) into y from db9.user where shell="/sbin/nologin";
-> set z=x+y;
-> select z;
-> end
-> //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql> call p6;
+------+
| z |
+------+
| 19 |
+------+
#创建存储过程p1 计算 传入参数 var1 和 var2 shell的 用户共有多少
mysql> drop procedure if exists p1;
mysql> delimiter //
mysql> create procedure p1(
in var1 char(20), in var2 char(25),out x int,out y int)
-> begin
-> declare z int;
-> set z=0;
-> select count(name) into x from db9.user where shell=var1;
-> select count(name) into y from db9.user where shell=var2;
-> set z=x+y;
-> select z;
-> end
-> //
Query OK, 0 rows affected (0.01 sec)
mysql> delimiter ;
#没有输出参数报错
mysql> call p1;
ERROR 1318 (42000): Incorrect number of arguments for PROCEDURE db9.p1; expected 4, got 0
mysql> call p1("/bin/bash","/sbin/nologin",@x,@y);
+------+
| z |
+------+
| 19 |
+------+
流程控制
条件测试
数值比较
| 类型 | 说明 |
|---|---|
= |
等于 |
> >= |
大于 大于或等于 |
< <= |
小于 小于或等于 |
!= |
不等于 |
| BETWEEN ... AND .. | 在 .. 与 .. 之间 |
示例
逻辑比较
| 类型 | 用途 |
|---|---|
OR AND ! |
逻辑或 逻辑与 逻辑非 |
IN ... NOT IN ... |
在 .. 范围内 不在 .. 范围内 |
IS NULL |
字段的值为空 |
IS NOT NULL |
字段的值不为空 |
LIKE |
模糊匹配 |
REGEXP |
正则匹配 |
示例
选择结构
语法
# 格式1 if
if 条件测试 then
代码 .. ..
.. ..
end if;
#格式2 if else
if 条件测试 then
代码1 .. ..
.. ..
else
代码2 .. ..
.. ..
end if;
示例
mysql> drop procedure if exists p4;
mysql> delimiter //
mysql> create procedure p4( in num int(2))
-> begin
-> if num <= 10 then
-> select id,name,shell from db9.user where id <=num;
-> end if;
-> end
-> //
mysql> delimiter ;
mysql> call p4(3);
+----+--------+---------------+
| id | name | shell |
+----+--------+---------------+
| 1 | tom | /bin/bash |
| 2 | bin | /sbin/nologin |
| 3 | daemon | /sbin/nologin |
+----+--------+---------------+
mysql> call p4(11);
Query OK, 0 rows affected (0.00 sec)
#if else end if
mysql> drop procedure if exists p5;
mysql> create procedure p5( in num int(2))
-> begin
-> if num is null then
-> select id,name,shell from db9.user where id =2;
-> else
-> select id,name,shell from db9.user where id<=num;
-> end if;
-> end
-> //
mysql> delimiter ;
mysql> set @x=null;
mysql> call p5(@x);
+----+------+---------------+
| id | name | shell |
+----+------+---------------+
| 2 | bin | /sbin/nologin |
+----+------+---------------+
mysql> call p5(2);
+----+------+---------------+
| id | name | shell |
+----+------+---------------+
| 1 | tom | /bin/bash |
| 2 | bin | /sbin/nologin |
+----+------+---------------+
循环结构
while 条件式循环
反复测试条件,只要成立就执行命令序列
while 条件判断 do
循环体
.. ..
end while;
示例
# 输出1-5
mysql> delimiter //
mysql> create procedure p10()
-> begin
-> declare i int(2);
-> set i=1;
-> while i<=5 do
-> select i;
-> set i=i+1;
-> end while;
-> end
-> //
mysql> delimiter ;
mysql> call p10();
+------+
| i |
+------+
| 1 |
+------+
+------+
| i |
+------+
| 2 |
+------+
+------+
| i |
+------+
| 3 |
+------+
+------+
| i |
+------+
| 4 |
+------+
+------+
| i |
+------+
| 5 |
+------+
#输出 uid 为偶数 的 id,name,uid
mysql> drop procedure if exists p6;
mysql> delimiter //
mysql> create procedure p6()
-> begin
-> declare i int(2);
-> declare j int(2);
-> declare z int(2);
#查看表总行数 行数 存入 i
-> select count(id) into i from db9.user;
->
# id 从1开始 放入变量j 每次自加1
-> set j=1;
-> while j<=i do
-> select uid into z from db9.user where id=j;
-> if z%2=0 then
-> select id,name,uid from db9.user where id=j;
-> end if;
-> set j=j+1;
-> end while;
-> end
-> //
mysql> delimiter ;
mysql> call p6();
+----+------+------+
| id | name | uid |
+----+------+------+
| 1 | tom | 0 |
+----+------+------+
1 row in set (0.00 sec)
+----+--------+------+
| id | name | uid |
+----+--------+------+
| 3 | daemon | 2 |
+----+--------+------+
1 row in set (0.00 sec)
+----+------+------+
| id | name | uid |
+----+------+------+
| 5 | lp | 4 |
+----+------+------+
1 row in set (0.00 sec)
+----+----------+------+
| id | name | uid |
+----+----------+------+
| 7 | shutdown | 6 |
+----+----------+------+
1 row in set (0.00 sec)
+----+------+------+
| id | name | uid |
+----+------+------+
| 9 | mail | 8 |
+----+------+------+
1 row in set (0.00 sec)
+----+-------+------+
| id | name | uid |
+----+-------+------+
| 11 | games | 12 |
+----+-------+------+
1 row in set (0.00 sec)
+----+------+------+
| id | name | uid |
+----+------+------+
| 12 | ftp | 14 |
+----+------+------+
1 row in set (0.00 sec)
+----+-----------------+------+
| id | name | uid |
+----+-----------------+------+
| 14 | systemd-network | 192 |
+----+-----------------+------+
1 row in set (0.00 sec)
+----+------+------+
| id | name | uid |
+----+------+------+
| 17 | sshd | 74 |
+----+------+------+
1 row in set (0.00 sec)
+----+------+------+
| id | name | uid |
+----+------+------+
| 19 | ntp | 38 |
+----+------+------+
1 row in set (0.00 sec)
+----+------+------+
| id | name | uid |
+----+------+------+
| 21 | rpc | 32 |
+----+------+------+
1 row in set (0.00 sec)
+----+-----------+-------+
| id | name | uid |
+----+-----------+-------+
| 23 | nfsnobody | 65534 |
+----+-----------+-------+
loop 死循环
loop
循环体
.. ..
end loop;
示例
#死循环 不按 ctrl + c 会一直执行.
drop procedure if exists p7;
delimiter //
create procedure p7()
begin
declare i int(2);
set i=1;
loop
select i;
set i=i+1;
end loop;
end
//
delimiter ;
call p7();
repeat 条件式循环
条件不成立时,执行循环,符合条件时,结束循环
repeat
循环体
.. ..
#untill 后面不需要使用;
until 条件判断
end repeat;
示例
mysql> drop procedure if exists p8;
mysql> delimiter //
mysql> create procedure p8()
-> begin
-> declare i int(2);
-> set i=1;
-> repeat
-> select i;
-> set i=i+1;
-> until i=3
-> end repeat;
-> end
-> //
mysql> delimiter ;
mysql> call p8();
+------+
| i |
+------+
| 1 |
+------+
1 row in set (0.00 sec)
+------+
| i |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
控制循环
| 选项 | 说明 | shell相似 |
|---|---|---|
| LEAVE 标签名 | 结束循环的执行 | break |
| ITERATE 标签名 | 结束当前循环,并执行下一次循环 | continue |
示例
drop procedure if exists p9;
delimiter //
create procedure p9()
begin
declare i int(2);
set i=0;
# 为循环设置 lab1 标签名
lab1:loop
set i=i+1;
if i=3 then
#跳出本次循环,继续下一次循环
ITERATE lab1;
end if;
if i=5 then
#结束循环执行
LEAVE lab1;
end if;
select i;
end loop;
end
//
delimiter ;