3. An object table has one column for each attribute of an object, plus one additional column. What is this additional column used for?
4. How is an object reference different from an object?
5. How many attributes must an object have? How many methods?
6. What datatypes are allowed for the return value of a MAP function?

Exercises

1. Write a stored function that creates and returns an object of type building. This function should accept as parameters the building's name, its address, and the manager's employee number. Have the function check the database before creating the new building object to be sure that another building with the same name does not already exist. If another building with the same name does exist, then the function should return null.
2. Modify the building object type definition to use a MAP function for comparisons instead of an ORDER function.