【转】MySQL随机字符串生成

DROP FUNCTION IF EXISTS rand_string;    

DELIMITER $$

CREATE FUNCTION rand_string(str_length TINYINT UNSIGNED, str_type TINYINT UNSIGNED) RETURNS VARCHAR(255)  
BEGIN  
    -- Function   : rand_string  
    -- Author     : reymondtu#opencfg.com  
    -- Date       : 2011/03/27  
    -- Params     : str_length int unsigned   
    --                  The random string length of random string  
    --              str_type   int unsigned  
    --                  The random string type  
    --                      1.0-9  
    --                      2.a-z  
    --                      3.A-Z  
    --                      4.a-zA-Z  
    --                      5.0-9a-zA-Z  
    --  
    -- Example    :  
    --  
    -- mysql> select rand_string(32,5) from dual;  
    -- +----------------------------------+  
    -- | rand_string(32,5)                |  
    -- +----------------------------------+  
    -- | HbPBz4DWSAiJNLt4SgExHVwQI34bI6mt |  
    -- +----------------------------------+  
    -- 1 row in set  
  
    DECLARE counter INT UNSIGNED DEFAULT 0;  
    DECLARE const_chars VARCHAR(64) DEFAULT '0123456789';  
    DECLARE result VARCHAR(255) DEFAULT '';  
   
    IF str_type = 1 THEN  
        SET const_chars = '0123456789';  
    ELSEIF str_type = 2 THEN  
        SET const_chars = 'abcdefghijklmnopqrstuvwxyz';  
    ELSEIF str_type = 3 THEN  
        SET const_chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';  
    ELSEIF str_type = 4 THEN  
        SET const_chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';  
    ELSEIF str_type = 5 THEN  
        SET const_chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';  
    ELSE  
        SET const_chars = '0123456789';  
    END IF;  
   
    WHILE counter < str_length DO    
        SET result = CONCAT(result,SUBSTR(const_chars,CEIL(RAND()*(LENGTH(const_chars)-1)),1));  
    SET counter = counter + 1;  
    END WHILE;  
  
    RETURN result;  
END  ;

$$
DELIMITER ;

转自：http://tuhaitao.iteye.com/blog/976936