数据库|mysql教程
MySQL
数据库-mysql教程
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本篇文章给大家带来的内容是关于MySQL自定义函数与存储过程的详细介绍（附代码），有一定的参考价值，有需要的朋友可以参考一下，希望对你有所帮助。
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1、前置条件
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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@ | 15103887470 | admin | male | 200 | -04-12 20:11:30 | -04-19 20:11:30 | 30 | NULL || 2 | StephenWang8 | 123456 | 123@ | 15103887470 | viewer | male | 200 | -04-12 20:11:30 | -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 （[参数1] [类型1], [参数N] [类型N]）returns return
调用UDF的语法如下：
select ([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
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 1mysql> 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 1mysql> 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 1mysql> 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 latin1return (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 ;
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 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 ( [过程参数[,…] ] ) [过程参数[,…] ] 格式[ IN | OUT | INOUT ] #语法定义来自：/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
show create procedure
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
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
4、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 #存储过程call
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。
