Hi,

I have this sample table:

CREATE TABLE `dummy` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `userId` int(11) NOT NULL,
  `pet` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ;


INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(1, 1, 'dog');
INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(2, 1, 'cat');
INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(3, 2, 'dog');
INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(4, 2, 'cat');
INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(5, 3, 'cat');
INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(6, 4, 'dog');

How can I write the statements below in mysql:

• Retrieve all users who own both a dog and a cat
• Retrieve all users who own a dog or a cat
• Retrieve all users who own only a cat
• Retrieve all users who doesn't own a cat

Thanks!