Database Design

Triggers, Apps, or CDC? Pros and Cons of 3 Data Audit Techniques

People are in your data. They’re looking at it, even changing it. Should they be stopped? Did they break something? If so, who broke it? When? These are common questions that come up (especially after someone breaks something), and DBAs are often called upon to solve the problem. Here are three great ways to start identifying your data gremlins: (more…)

Boyce/Codd Normal Form (BCNF)

In my article on 3NF we saw that it was the same as 2NF but with one additional restriction. BCNF, similarly, is 3NF with one more restriction:
BCNF:

“Relvar R is in Boyce/Codd normal form (BCNF) if and only if, for every nontrivial FD XY that holds in R, X is a superkey.”
Date, C.J. Database Design & Relational Theory. Sebastopol: O,Reilly Media, Inc., 2012. Print. (Emphasis theirs)

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First Normal Form (1NF)

Definition

Each row contains one value, of the appropriate type, for each column, and there are no duplicate rows.

This is a simple rewording of the formal definition:

Let relation r have attributes A1, …, An, of types T1, …, Tn, respectively. Then r is in first normal form (1NF) if and only if, for all tuples t appearing in r, the value of attribute Ai in t is of type Ti (i= 1, …, n).”
Date, C.J. Database Design & Relational Theory. Sebastopol: O,Reilly Media, Inc., 2012. Print. (Emphasis theirs)

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