Answer to Problem 2.7

SSN is not a good identifier unless the set of all people in the database consists of employed people in the United States. People not in this set might not have a SSN. This means that SSN could not be used to uniquely identify each person. As for using name as an identifier: this is also a bad idea since a person's name can change through his or her life for a variety of reasons. An entity's identifier should never change.

Return to details of ER modeling.

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License