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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
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
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 |
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
select < 函数名 > | |
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。
:
