无需复合键即可归一化为1NF

Question

Its often stated that to reach 1nf, a new entity has to be created and that entity has to have a composite key .

LeadID | leadDate | Name | DOB | streetAddress | city | state | residenceType

If I was to normalize streetAddress, city, state, residenceType into a new entity, I would have to create a new primary key right then and there. I cannot use LeadID because that would mean that addresses cannot be created without a lead, which is not true. And I cannot use streetAddress because the streets are not good candidates (5123 glowsville way st. n ave. is not a good key at all).

So I am forced to simply create a key for this new entity. Is this alright?

Answer 1

First normal form means:

A relation is in first normal form if the domain of each attribute contains only atomic values, and the value of each attribute contains only a single value from that domain.

So unless you're storing multiple streets in the streetAddress column, you are already complying with first normal form.

Answer 2

1NF has nothing to do with the presence of composite keys. To satisfy 1NF a table must be an accurate representation of a relation and therefore must have at least one candidate key , which may or may not include composite keys.

Possibly you have in mind the Universal Relation Assumption , a concept in database design theory that is sometimes used to teach normalization by decomposition. The URA assumes that a relation exists from which all the desired relations can be obtained by nonloss decomposition. The universal relation typically has a composite key. Note that the URA is itself controversial and definitely questionable but it is one way to think about problems in design theory.

Normalization theory strictly never requires the introduction of new attributes. In principle the attributes and dependencies are assumed to be a given.