MySQL自定义函数和存储过程示例详解

前言

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1、前置条件

MySQL数据库中存在表user_info，其结构和数据如下：

									mysql> desc user_info;

									+-----------+----------+------+-----+---------+-------+

									| Field | Type | Null | Key | Default | Extra |

									+-----------+----------+------+-----+---------+-------+

									| id | int(10) | NO | PRI | NULL | |

									| name | char(20) | NO | | NULL | |

									| passwd | char(40) | NO | | NULL | |

									| email | char(20) | NO | | NULL | |

									| phone | char(20) | NO | | NULL | |

									| role | char(10) | NO | | NULL | |

									| sex | char(10) | NO | | NULL | |

									| status | int(10) | NO | | NULL | |

									| createAt | datetime | NO | | NULL | |

									| exprAt | datetime | NO | | NULL | |

									| validDays | int(10) | NO | | NULL | |

									| delAt | datetime | YES | | NULL | |

									+-----------+----------+------+-----+---------+-------+

									12 rows in set (0.10 sec)

									mysql> select * from user_info;

									+----+--------------+----------+------------+-------------+--------+------+--------+---------------------+---------------------+-----------+-------+

									| id | name  | passwd | email | phone | role | sex | status | createAt  | exprAt  | validDays | delAt |

									+----+--------------+----------+------------+-------------+--------+------+--------+---------------------+---------------------+-----------+-------+

									| 1 | StephenWang7 | py123456 | 123@qq.com | 15103887470 | admin | male | 200 | 2019-04-12 20:11:30 | 2019-04-19 20:11:30 | 30 | NULL |

									| 2 | StephenWang8 | 123456 | 123@qq.com | 15103887470 | viewer | male | 200 | 2019-04-12 20:11:30 | 2019-04-19 20:11:30 | 30 | NULL |

									+----+--------------+----------+------------+-------------+--------+------+--------+---------------------+---------------------+-----------+-------+

									2 rows in set (0.00 sec)

2、自定义函数

函数：可以完成特定功能的一段SQL集合。MySQL支持自定义函数来完成特定的业务功能。

创建自定义函数（User Defined Function 简称UDF）的语法如下：

create function <函数名称> （[参数1] [类型1], [参数N] [类型N]）
returns <类型>
return
<函数主体>

调用UDF的语法如下：

select <函数名称> ([参数])

创建无参的UDF

示例1：查询user_info表中有多少条记录

									#定义函数

									mysql> create function user_info_count()

									 -> returns int(10)

									 -> return

									 -> (select count(*) from user_info);

调用函数user_info_count()

									mysql> select user_info_count();

									+-------------------+

									| user_info_count() |

									+-------------------+

									|   2 |

									+-------------------+

									1 row in set (0.00 sec)

创建有参UDF

示例2：根据id查询用户name。

									#定义函数

									mysql> create function queryNameById(uid int(10))

									 -> returns char(20)

									 -> return

									 -> (select name from user_info where id=uid);

									Query OK, 0 rows affected (0.01 sec)

调用函数，查询id为1的用户名称。

									mysql> select queryNameById(1);

									+------------------+

									| queryNameById(1) |

									+------------------+

									| StephenWang7 |

									+------------------+

									1 row in set (0.00 sec)

查看UDF

查询系统中所有的UDF

1	`show` `function` `status;`

查询指定的UDF

									#

									show create function 函数名称;

									mysql> show function queryNameById;

									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 'queryNameById' at line 1

									mysql> show function queryNameById();

									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 'queryNameById()' at line 1

									mysql> show create function queryNameById();

									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 '()' at line 1

									mysql> show create function queryNameById;

									+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+

									| Function | sql_mode                 | Create Function                  | character_set_client | collation_connection | Database Collation |

									+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+

									| queryNameById | 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 | CREATE DEFINER=`root`@`localhost` FUNCTION `queryNameById`(uid int(10)) RETURNS char(20) CHARSET latin1

									return (select name from user_info where id=uid) | utf8   | utf8_general_ci | latin1_swedish_ci |

									+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+

									1 row in set (0.00 sec

修改UDF

如果想要修改函数的内容，先删除后再重新创建。

删除UDF

删除UDF语法如下：

drop function <函数名称>;

示例3：删除函数queryNameId后再次调用并观察现象。

									mysql> drop function queryNameById;

									Query OK, 0 rows affected (0.45 sec)

									mysql> select queryNameById(1);

									ERROR 1305 (42000): FUNCTION rms.queryNameById does not exist

									mysql>

3、存储过程

存储功能和自定义函数相似，也是一组完成特定功能的SQL语句集合。把复杂或频繁调用的SQL提前写好并指定一个名称。待到要使用时，直接调用即可。

定义存储过程的语法如下：

CREATE PROCEDURE <过程名> ( [过程参数[,…] ] ) <过程体>
[过程参数[,…] ] 格式
[ IN | OUT | INOUT ] <参数名> <类型>
#语法定义来自：http://c.biancheng.net/view/2593.html

创建无参的存储过程

示例4：查询用户name。

									mysql> DELIMITER //

									mysql> craete procedure queryName()

									 -> begin

									 -> select name from user_info;

									 -> end //

关于DELIMITER命令，修改MySQL结束命令的字符。默认的结束命令字符为分号，当存储过程中包含多条语句时，遇到第一个分号会作为存储过程结束的标志。这样不符合预期，因此需要修改默认结束命令字符。 DELIMITER //就是将结束命令字符修改为//。调用存储过程的命令为：call 存储过程名称。

									#此时的命令的结束符号为// 不是;

									mysql> call queryName()//

									+--------------+

									| name   |

									+--------------+

									| StephenWang7 |

									| StephenWang8 |

									+--------------+

									2 rows in set (0.00 sec)

									Query OK, 0 rows affected (0.00 sec)

创建带参数的存储过程

示例5：根据id查询name。

									mysql> create procedure queryNameById

									 -> (In uid int(15))

									 -> begin

									 -> select name from user_info where id=uid;

									 -> end

									 -> //

									Query OK, 0 rows affected (0.03 sec)

调用存储过程queryNameById

									mysql> call queryNameById(1);

									 -> //

									+--------------+

									| name   |

									+--------------+

									| StephenWang7 |

									+--------------+

									1 row in set (0.03 sec)

									Query OK, 0 rows affected (0.04 sec)

修改存储过程

如果想创建存储过程的内容可以先删除再重新创建存储过程。

查看存储过程

1	`show` `create` `procedure` `<过程名称>`

mysql> show create procedure queryNameById; -> // +

---------------+-------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+ | Procedure | sql_mode | Create Procedure | character_set_client | collation_connection | Database Collation | +---------------+-------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+ | queryNameById | 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 | CREATE DEFINER=`root`@`localhost` PROCEDURE `queryNameById`(In uid int(15)) begin select name from user_info where id=uid; end | utf8 | utf8_general_ci | latin1_swedish_ci | +---------------+-------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+ 1 row in set (0.04 sec)

删除存储过程

drop procedure <过程名称>

删除存储过程queryNameById

									mysql> drop procedure queryNameById//

									Query OK, 0 rows affected (0.02 sec)

									mysql> call queryNameById(1)//

									ERROR 1305 (42000): PROCEDURE rms.queryNameById does not exist