et lux in tenebris lucet

Last year when I was searching for ways to overcome the lack of built-in IPv6 functions in MySQL, I was curious how other people were solving the problem. There are solutions out there that store IPv6 addresses across two database fields, but I find this unwieldy and prefer storing them as a single value. This was by far the most elegant solution I found that doesn’t rely on external dependencies (like writing special functions for your program to handle the two-value method):

http://oierud.name/bliki/IPv6AdressesAndMysql.html

Basically, it duplicates the capabilities of the built-in IPv4 INET_ATON() and INET_NTOA() counterparts. And case the URL ever goes dead:

DELIMITER //
CREATE FUNCTION INET_ATON6(n CHAR(39))
RETURNS DECIMAL(39) UNSIGNED
DETERMINISTIC
BEGIN
    RETURN CAST(CONV(SUBSTRING(n FROM  1 FOR 4), 16, 10) AS DECIMAL(39))
                       * 5192296858534827628530496329220096 -- 65536 ^ 7
         + CAST(CONV(SUBSTRING(n FROM  6 FOR 4), 16, 10) AS DECIMAL(39))
                       *      79228162514264337593543950336 -- 65536 ^ 6
         + CAST(CONV(SUBSTRING(n FROM 11 FOR 4), 16, 10) AS DECIMAL(39))
                       *          1208925819614629174706176 -- 65536 ^ 5
         + CAST(CONV(SUBSTRING(n FROM 16 FOR 4), 16, 10) AS DECIMAL(39)) 
                       *               18446744073709551616 -- 65536 ^ 4
         + CAST(CONV(SUBSTRING(n FROM 21 FOR 4), 16, 10) AS DECIMAL(39))
                       *                    281474976710656 -- 65536 ^ 3
         + CAST(CONV(SUBSTRING(n FROM 26 FOR 4), 16, 10) AS DECIMAL(39))
                       *                         4294967296 -- 65536 ^ 2
         + CAST(CONV(SUBSTRING(n FROM 31 FOR 4), 16, 10) AS DECIMAL(39))
                       *                              65536 -- 65536 ^ 1
         + CAST(CONV(SUBSTRING(n FROM 36 FOR 4), 16, 10) AS DECIMAL(39))
         ;
END;
//
DELIMITER ;

DELIMITER //
CREATE FUNCTION INET_NTOA6(n DECIMAL(39) UNSIGNED)
RETURNS CHAR(39)
DETERMINISTIC
BEGIN
  DECLARE a CHAR(39)             DEFAULT '';
  DECLARE i INT                  DEFAULT 7;
  DECLARE q DECIMAL(39) UNSIGNED DEFAULT 0;
  DECLARE r INT                  DEFAULT 0;
  WHILE i DO
    -- DIV doesn't work with nubers > bigint
    SET q := FLOOR(n / 65536);
    SET r := n MOD 65536;
    SET n := q;
    SET a := CONCAT_WS(':', LPAD(CONV(r, 10, 16), 4, '0'), a);

    SET i := i - 1;
  END WHILE;

  SET a := TRIM(TRAILING ':' FROM CONCAT_WS(':',
                                            LPAD(CONV(n, 10, 16), 4, '0'),
                                            a));

  RETURN a;

END;
//
DELIMITER ;