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_9

9. JDs and 5NF (Informal)

C. J. Date¹ 

(1)

Healdsburg, California, USA

 

If you can’t beat ’em, join ’em.

—Anon.

Just as Boyce/Codd normal form is defined in terms of functional dependencies, so fifth normal form (5NF) is defined in terms of join dependencies (JDs);¹ as noted in Chapter 4, in fact, 5NF is the normal form with respect to JDs, just as BCNF is the normal form with respect to FDs. And the treatment of these ideas in this part of the book therefore parallels the treatment of BCNF and FDs in Part II. In other words, I plan to treat the material both formally, in Chapter 10, and informally in the present chapter.

Let me immediately ...