What is a good KISS description of Boyce-Codd normal form?

Question

What is a KISS (Keep it Simple, Stupid) way to remember what Boyce-Codd normal form is and how to take a unnormalized table and BCNF it?

Wikipedia\'s info: not terribly

Answer 1

Here are some helpful excerpts from the Wikipedia page on Third Normal Form:

Bill Kent defines Third Normal Form this way:

Each non-key attribute "must provide a fact about the key, the whole key, and nothing but the key."

Requiring that non-key attributes be dependent on "the whole key" ensures that a table is in 2NF; further requiring that non-key attributes be dependent on "nothing but the key" ensures that the table is in 3NF.

Chris Date adapts Kent's mnemonic to define Boyce-Codd Normal Form:

"Each attribute must represent a fact about the key, the whole key, and nothing but the key." Here the requirement is concerned with every attribute in the table, not just non-key attributes.

This comes into play when a table has multiple compound candidate keys, and an attribute within one candidate keys has a dependency on a part of another candidate key. Third Normal Form wouldn't prohibit this, because it excludes key attributes. But BCNF applies the rule to key attributes as well.

As for how to make a table satisfy BCNF, you need to represent the extra dependency, with another attribute and possibly by splitting attributes into another table.