MySQL's UUID
function returns a UUIDv1 GUID. I'm looking for an easy way to generate random GUIDs (i.e. UUIDv4) in SQL.
I've spent quite some time looking for a solution and came up with the following mysql function that generates a random UUID (i.e. UUIDv4) using standard MySQL functions. I'm answering my own question to share that in the hope that it'll be useful.
-- Change delimiter so that the function body doesn't end the function declaration
DELIMITER //
CREATE FUNCTION uuid_v4()
RETURNS CHAR(36) NO SQL
BEGIN
-- Generate 8 2-byte strings that we will combine into a UUIDv4
SET @h1 = LPAD(HEX(FLOOR(RAND() * 0xffff)), 4, '0');
SET @h2 = LPAD(HEX(FLOOR(RAND() * 0xffff)), 4, '0');
SET @h3 = LPAD(HEX(FLOOR(RAND() * 0xffff)), 4, '0');
SET @h6 = LPAD(HEX(FLOOR(RAND() * 0xffff)), 4, '0');
SET @h7 = LPAD(HEX(FLOOR(RAND() * 0xffff)), 4, '0');
SET @h8 = LPAD(HEX(FLOOR(RAND() * 0xffff)), 4, '0');
-- 4th section will start with a 4 indicating the version
SET @h4 = CONCAT('4', LPAD(HEX(FLOOR(RAND() * 0x0fff)), 3, '0'));
-- 5th section first half-byte can only be 8, 9 A or B
SET @h5 = CONCAT(HEX(FLOOR(RAND() * 4 + 8)),
LPAD(HEX(FLOOR(RAND() * 0x0fff)), 3, '0'));
-- Build the complete UUID
RETURN LOWER(CONCAT(
@h1, @h2, '-', @h3, '-', @h4, '-', @h5, '-', @h6, @h7, @h8
));
END
//
-- Switch back the delimiter
DELIMITER ;
Note: The pseudo-random number generation used (MySQL's RAND
) is not
cryptographically secure and thus has some bias which can increase the collision
risk.