Nullology: The Zen of Database
Nullology is the study of the empty set. Of course, sets crop up all over the place in the database world; but the question is - and it's a crucial one - what happens if the set under consideration happens to be empty? For example, a relation contains a set of tuples: what about the possibility of a relation containing no tuples at all? Now this particular possibility is a familiar one, because a relation with no tuples is much like a conventional empty file.