MySQL自定义函数与存储历程的细致介绍（附代码）
发布时间：08/01 来源：未知 浏览：
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1、前置前提
MySQL数据库中存在表user_info，其构造和数据如下：
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汇合。MySQL支撑自定义函数来完成特定的业务功能。
新建自定义函数（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>
调取UDF的语法如下：
select <函数名称> ([参数])
新建无参的UDF
示例1：查询user_info表中有多少笔记录
#定义函数
mysql> create function user_info_count()
-> returns int(10)
-> return
-> (select count(*) from user_info);调取函数user_info_count()
mysql> select user_info_count(); +-------------------+ | user_info_count() | +-------------------+ | 2 | +-------------------+ 1 row in set (0.00 sec)
新建有参UDF
示例2：依据id查询会员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)调取函数，查询id为1的会员名称。
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
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
要是想要修改函数的内容，先删除后再从新新建。
删除UDF
删除UDF语法如下：
drop function <函数名称>;
示例3：删除函数queryNameId后再次调取并调查现象。
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、存储历程
存储功能和自定义函数类似，也是一组完成特定功能的SQL语句汇合。把复杂或频繁调取的SQL提早写好并指定一个名称。待到要运用时，直接调取即可。
定义存储历程的语法如下：
CREATE PROCEDURE <过程名> ( [历程参数[,…] ] ) <过程体> [历程参数[,…] ] 格局 [ IN | OUT | INOUT ] <参数名> <类型> #语法定义来自：http://c.biancheng.net/view/2593.html
新建无参的存储历程
示例4：查询会员name。
mysql> DELIMITER //
mysql> craete procedure queryName()
-> begin
-> select name from user_info;
-> end //对于DELIMITER下令，修改MySQL完毕下令的字符。默许的完毕下令字符为分号，当存储历程中包括多条语句时，碰到首先个分号会作为存储历程完毕的标记。这样不相符预测，因而需要修改默许完毕下令字符。 DELIMITER //就是将完毕下令字符修改为//。调取存储历程的下令为：call 存储历程名称。
#此时的下令的完毕符号为// 不是; mysql> call queryName()// +--------------+ | name | +--------------+ | StephenWang7 | | StephenWang8 | +--------------+ 2 rows in set (0.00 sec) Query OK, 0 rows affected (0.00 sec)
新建带参数的存储历程
示例5：依据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)调取存储历程queryNameById
mysql> call queryNameById(1);
-> //
+--------------+
| name |
+--------------+
| StephenWang7 |
+--------------+
1 row in set (0.03 sec)
Query OK, 0 rows affected (0.04 sec)修改存储历程
要是想新建存储历程的内容可以先删除再从新新建存储历程。
查看存储历程
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)
删除存储历程
drop procedure <过程名称>
删除存储历程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
4、总结
自定义函数和存储历程都是完成特定功能的SQL汇合，那么他们有什么不一样呢？
a、调取方式不一样
#自定义函数 select <函数名> #存储历程 call <存储过程名>
b、自定义函数不克不及有输出参数，而存储历程可以。
c、自定义函数必需要包括return语句，而存储历程则不需要。
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