Question:
Can we use the extended relational algebra, or just the core?
Answer:
You may use the extended algebra unless we say otherwise.
Question:
Should we assume relational algebra is an algebra of sets or bags?
Answer:
Sets, unless we ask for the bag version explicitly.
Question:
In problem 6, do we need to justify our answer?
Answer:
I forgot to require an explanation, but I think people should give a
brief explanation. It's not hard, once you see what the right answer is.
Question:
In problem 2(b), does ``any'' really mean ``exists''?
Answer:
No; the intention was coloquial.
We're really asking if the employee makes more than every manager.
Question:
How should we express our relational-algebra expressions?
Answer:
Any of the notations we used in class is OK: trees, plain old expressions, or
the linear sequence of assignments.