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MySQL自定义函数与存储过程

2019年04月14日 07:31  | 萬仟网IT编程  | 我要评论

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

#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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