語法

自定義函數也需要相應的要求，語法如下:

CREATE FUNCTION(參數列表)

RETURNS返回值類型

函數體

刪除:

DROPFUNCTION

調用自定義函數語法:

SELECT (parameter_value,...)

語法實例 create function rand_string(n int) returns varchar(255)

begin

declare chars_str varchar(100) default 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';

declare return_str varchar(255) default '';

declare i int default 0;

while i < n do

set return_str = concat(return_str, substring(chars_str,floor(1+rand()*62),1));

set i= i+1;

end while;

return return_str;

end;

效果

這樣我們自己定義的函數就完成了，先來看看FUNCTION屬性及運行效果； mysql> show function status;

+------+-------------+----------+----------------+---------------------+---------------------+---------------+---------+----------------------+----------------------+--------------------+

| Db | Name | Type | Definer | Modified | Created | Security_type | Comment | character_set_client | collation_connection | Database Collation |

+------+-------------+----------+----------------+---------------------+---------------------+---------------+---------+----------------------+----------------------+--------------------+

| test | rand_string | FUNCTION | root@localhost | 2017-05-26 14:13:10 | 2017-05-26 14:13:10 | DEFINER | | utf8 | utf8_general_ci | latin1_swedish_ci |

+------+-------------+----------+----------------+---------------------+---------------------+---------------+---------+----------------------+----------------------+--------------------+

1 row in set

mysql> show create function rand_string;

+-------------+------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+

| Function | sql_mode | Create Function | character_set_client | collation_connection | Database Collation |

+-------------+------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+

| rand_string | NO_ENGINE_SUBSTITUTION | CREATE DEFINER=`root`@`localhost` FUNCTION `rand_string`(n int) RETURNS varchar(255) CHARSET latin1

begin

declare chars_str varchar(100) default 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';

declare return_str varchar(255) default '';

declare i int default 0;

while i < n do

set return_str = concat(return_str, substring(chars_str,floor(1+rand()*62),1));

set i= i+1;

end while;

return return_str;

end | utf8 | utf8_general_ci | latin1_swedish_ci |

+-------------+------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+

1 row in set

mysql> select rand_string(100);

+------------------------------------------------------------------------------------------------------+

| rand_string(100) |

+------------------------------------------------------------------------------------------------------+

| bfvEBTvGJqOBp7ajTm0KAwIPQy7Mmighp2PTN86XmIoCJG2YBYQbbciKG1Tfo3YvsDEaIVhwBhp2QY7xa3ADfd8SNctzjGjlCTuA |

+------------------------------------------------------------------------------------------------------+

1 row in set

名詞解釋

接下來對上面所涉及到的關鍵詞進行匯總整理。

大寫

小寫

詞義

用法

USE

use

切換數據庫

use test

IF EXIST

if exist

判斷是否存在

if exist name

DELIMITER

delimiter

定義結束符

delimiter //        默認為；

DEFINER

definer

權限

definer=root@localhost

CHARSET

charset

編碼

charset =utf8

DECLARE

declare

聲明

declare return_str varchar(10240)

DEFAULT

default

默認值

default 'abcdefgh';

ENGINE

engine

存儲引擎

engine=innodb||engine=myisam

FUNCTION

function

函數

function rand_string(n INT)

RETURNS

returns

返回類型

returns varchar(10240)

RETURN

return

返回值

return 'zhangsan'

CONCAT

concat

拼串

concat(string value,string value)

SUBSTRING

substring

截取字符串

substring(被截取名,開始索引，結束索引)

FLOOR

floor

取整

floor(23.33)

RAND

rand

隨機數

rand()

WHILE..DO

while..do

while循環

while i

SHOW..STATUS

show..status

查看運行狀態

show function status；