Database denormalization

- So we should always take our database design…through the First, Second, and Third Normal Forms.…There are more criteria available.…There are Fourth, Fifth, and Sixth Normal Forms.…There's something called Boyce-Codd Normal Form,…but taking it to Third Normal Form…is the usual expectation in a business environment…and certainly all we need to cover…in a course like this one.…And you will actually find that a lot of tables out there…intentionally break normalization rules…and some others seem like they do, but they actually don't.…

Here's one example.…Let's say we've got an Employee table…and I'm storing an email and a phone number.…Well, what happens if I want to add…another email address, another phone number?…Technically this can be described as…breaking First Normal Form.…It's a repeating group.…But in practice, you may find it…more convenient to just allow an Email,…and Email2 column, or perhaps a home phone…and mobile phone column, rather than splitting…everything out into multiple tables…and having to follow relationships…