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1、前置条件
MySQL数据库中存在表user_info，其构造和数据以下：
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：能够完成特定功用的一段SQL鸠合。MySQL支撑自定义函数来完成特定的营业功用。
建立自定义函数（User Defined Function 简称UDF）的语法以下：
create function <函数称号> （[参数1] [范例1], [参数N] [范例N]） returns <范例> return <函数主体>
挪用UDF的语法以下：
select <函数称号> ([参数])
建立无参的UDF
示例1：查询user_info表中有若干条纪录
#定义函数
mysql> create function user_info_count()
-> returns int(10)
-> return
-> (select count(*) from user_info);
挪用函数user_info_count()
mysql> select user_info_count(); +-------------------+ | user_info_count() | +-------------------+ | 2 | +-------------------+ 1 row in set (0.00 sec)
建立有参UDF
示例2：依据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)
挪用函数，查询id为1的用户称号。
mysql> select queryNameById(1); +------------------+ | queryNameById(1) | +------------------+ | StephenWang7 | +------------------+ 1 row in set (0.00 sec)
检察UDF
查询体系中所有的UDF
show function status;
查询指定的UDF
# show create function 函数称号; 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
修正UDF
假如想要修正函数的内容，先删除后再从新建立。
删除UDF
删除UDF语法以下：
drop function <函数称号>;
示例3：删除函数queryNameId后再次挪用并视察征象。
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
存储功用和自定义函数类似，也是一组完成特定功用的SQL语句鸠合。把庞杂或频仍挪用的SQL提早写好并指定一个称号。待到要使用时，直接挪用即可。
定义存储历程的语法以下：
CREATE PROCEDURE <历程名> ( [历程参数[,…] ] ) <历程体> [历程参数[,…] ] 花样 [ IN | OUT | INOUT ] <参数名> <范例> #语法定义来自：http://c.biancheng.net/view/2593.html
建立无参的存储历程
示例4：查询用户name。
mysql> DELIMITER //
mysql> craete procedure queryName()
-> begin
-> select name from user_info;
-> end //
关于DELIMITER敕令，修正MySQL完毕敕令的字符。默许的完毕敕令字符为分号，当存储历程当中包括多条语句时，碰到第一个分号会作为存储历程完毕的标志。如许不符合预期，因而需要修正默许完毕敕令字符。 DELIMITER //就是将完毕敕令字符修正为//。挪用存储历程的敕令为：call 存储历程称号。
#此时的敕令的完毕符号为// 不是; mysql> call queryName()// +--------------+ | name | +--------------+ | StephenWang7 | | StephenWang8 | +--------------+ 2 rows in set (0.00 sec) Query OK, 0 rows affected (0.00 sec)
建立带参数的存储历程
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)
挪用存储历程queryNameById
mysql> call queryNameById(1);
-> //
+--------------+
| name |
+--------------+
| StephenWang7 |
+--------------+
1 row in set (0.03 sec)
Query OK, 0 rows affected (0.04 sec)
修正存储历程
假如想建立存储历程的内容能够先删除再从新建立存储历程。
检察存储历程
show create procedure <历程称号>
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 <历程称号>
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用的SQL鸠合，那末他们有什么差别呢？
a、挪用体式格局差别
#自定义函数 select <函数名> #存储历程 call <存储历程名>
b、自定义函数不能有输出参数，而存储历程能够。
c、自定义函数必需要包括return语句，而存储历程则不需要。
【相干引荐：MySQL教程】
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