/* Are there any big dogs? */
SELECT * 
FROM dog 
WHERE size = 'big';

/* What dogs are with people wearing caps? */
SELECT dog.size, dog.colour
FROM  dog, onLead, person
WHERE 	dog.dogId = onLead.dog 
	AND onLead.person = person.personID
	AND person.hat = 'cap';

/* Does anyone have more than one dog? */
SELECT personID
FROM person
WHERE (SELECT COUNT(*)
	FROM onLead,dog
	WHERE onLead.person = person.personID 
	AND onLead.dog = dog.dogID)  > 1;

/* Is anybody wearing an item of clothing the same 
   colour as (one of) their dog(s)? */

/* EXERCISE ! */