CREATE TABLE IF NOT EXISTS `test` (
  `field1` VARCHAR(50) NOT NULL,
  `field2` INT(11) DEFAULT NULL,
  `field3` INT(11) DEFAULT NULL,
  UNIQUE KEY `unique1` (`field1`,`field2`),
  UNIQUE KEY `unique2` (`field1`,`field3`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO `test` (`field1`, `field2`, `field3`) VALUES
    ('test', NULL, NULL),
    ('test', 1, NULL),
    ('test', NULL, 1),
    ('test', NULL, NULL),
    ('testing', 1, NULL);