CS145 - Spring 2003
Introduction to Databases

Online (OTC) Account Information

Please email course staff at cs145@cs.stanford.edu for further assistance with your OTC account. To have your password reset, just send your account login (the cs145_user one) with your request. You should never send a password, and staff should never ask for it. (Keep the last line in mind; it is often true of good security systems in the real world.)

Homework 4 Questions and Answers

• When asking a question about OTC problem text or answer choices, please quote the relevant portions of the assignment.
• After you complete a submission, please keep a copy of the entire Web page with your score and submission certificate. In case of data loss, you may be asked to present the page for your highest-scoring submission in order to restore your high score.

• In the question asking which CHECK constraints allow (4,4,4) to be inserted into a relation, some of the proposed constraints fail for the tuples given in the question for the relation. A real database would not allow the given tuples to appear, but please ignore the incongruity when answering the question, and imagine the given tuples really are there somehow. More specifically, please imagine that each proposed constraint is actually appended by OR (a = b AND b = c AND (a = 1 OR a = 2 OR a = 3)) or some other such condition allowing the three given tuples to appear. Thank you to Michael Kepe for pointing out this error.

CS145 Web pages - email the staff