Database Design and Relational Theory: Normal Forms and All That Jazz

© C. J. Date 2019

C. J. DateDatabase Design and Relational Theoryhttps://doi.org/10.1007/978-1-4842-5540-7_12

12. MVDs and 4NF

C. J. Date¹ 

(1)

Healdsburg, California, USA

 

Who’s on first, What’s on second, I Don’t Know’s on third.

—Bud Abbott and Lou Costello: The Naughty Nineties (1945)

In Chapter 10, I said that 4NF, like 2NF and 3NF, is mostly of historical interest. However, that characterization is possibly a little unfair, because:

• First of all, 4NF is the normal form with respect to what are called multivalued dependencies or MVDs. Now, MVDs are really just a special kind of JD; so if you know about JDs in general, you know about MVDs as well, in a sense. Nevertheless, MVDs are still worth studying in their own right (for one thing, they’re ...