安全に使える乱数を生成する関数

MySQLで簡単に乱数を生成する関数。

DELIMITER $$
CREATE FUNCTION randomString(len INT)
RETURNS tinytext
BEGIN
    declare r tinytext;
    declare s tinytext default '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    declare n int;
    set r='';
    while length(r) < len do
    set n=rand() * 61;
    set r=concat(r,substr(s,n,1));
    end while;
    RETURN r;
END$$
DELIMITER ;

例

mysql> select randomString(10);
+------------------+
| randomString(10) |
+------------------+
| BL446jgqlr       |
+------------------+
1 row in set (0.01 sec)

mysql> select randomString(4);
+-----------------+
| randomString(4) |
+-----------------+
| cEHA            |
+-----------------+
1 row in set (0.00 sec)

mysql>