Find the greatest common factor of two positive integers.
CREATE FUNCTION gcd(x int, y int) RETURNS int DETERMINISTIC
BEGIN
DECLARE dividend int;
DECLARE divisor int;
DECLARE remainder int;
SET dividend := GREATEST(x, y);
SET remainder := LEAST(x, y);
WHILE remainder != 0 DO
SET divisor = remainder;
SET remainder = MOD(dividend, divisor);
SET dividend = divisor;
END WHILE;
RETURN divisor;
END
