mysql生成随机数

DROP FUNCTION IF EXISTS rand_string;delimiter //CREATE FUNCTION rand_string(l_num tinyint UNSIGNED,l_type tinyint UNSIGNED)RETURNS varchar(127)BEGIN -- Function : rand_string -- Author   : dbachina#dbachina.com -- Date     : 2010/5/30 -- l_num : The length of random string -- l_type: The string type --         1.0-9 --         2.a-z --         3.A-Z --         4.a-zA-Z --         5.0-9a-zA-Z --  :  -- mysql> select rand_string(12,5) random_string;  -- +---------------+  -- | random_string |  -- +---------------+  -- | 3KzGJCUJUplw  |  -- +---------------+  -- 1 row in set (0.00 sec) DECLARE i int UNSIGNED DEFAULT 0; DECLARE v_chars varchar(64) DEFAULT '0123456789';  DECLARE result varchar ( 255) DEFAULT '';  IF l_type = 1 THEN    SET v_chars = '0123456789';  ELSEIF l_type = 2 THEN    SET v_chars = 'abcdefghijklmnopqrstuvwxyz';  ELSEIF l_type = 3 THEN    SET v_chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';  ELSEIF l_type = 4 THEN    SET v_chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';  ELSEIF l_type = 5 THEN    SET v_chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';  ELSE    SET v_chars = '0123456789';  END IF;  WHILE i < l_num DO      SET result = concat( result,substr(v_chars,ceil(rand()*(length(v_chars)-1)),1) );    SET i = i + 1;  END WHILE;  RETURN result;END;//delimiter ;

转自http://www.dbachina.com/2010/05/31/mysql_random_string_function/