MySQL自定义函数与存储过程的详细介绍（附代码）

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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> descuser_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* fromuser_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 functionuser_info_count()-> returns int(10)-> return-> (selectcount(*) from user_info);调用函数user_info_count()mysql> selectuser_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 functionqueryNameById(uid int(10))-> returns char(20)-> return-> (selectnamefromuser_infowhere 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> selectqueryNameById(1);+------------------+| queryNameById(1) |+------------------+| StephenWang7|+------------------+1 row in set (0.00 sec)查看UDF查询系统中所有的UDFshow function status;查询指定的UDF#showcreate function函数名称;mysql> showfunctionqueryNameById;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 1mysql> showfunctionqueryNameById();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 1mysql> showcreate functionqueryNameById();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 1mysql> showcreate functionqueryNameById;+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+| 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 latin1return (selectnamefromuser_infowhere 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> dropfunction queryNameById;Query OK, 0 rows affected (0.45 sec)mysql> select queryNameById(1);ERROR 1305 (42000): FUNCTION rms.queryNameById does not existmysql>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-> selectname 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> callqueryName()//+--------------+| 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 procedurequeryNameById-> (In uid int(15))-> begin-> selectnamefromuser_info where id=uid;-> end-> //Query OK, 0 rows affected (0.03 sec)调用存储过程queryNameByIdmysql> 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queryNameByIdmysql> drop procedurequeryNameById//Query OK, 0 rows affected (0.02 sec)mysql> callqueryNameById(1)//ERROR 1305 (42000): PROCEDURE rms.queryNameById does not exist4、总结自定义函数和存储过程都是完成特定功能的SQL集合，那么他们有什么不同呢？a、调用方式不同#自定义函数select<函数名>#存储过程call <存储过程名>b、自定义函数不能有输出参数，而存储过程可以。c、自定义函数必须要包含return语句，而存储过程则不需要。

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