【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