Re: erd to db

"Daniel Guntermann" <guntermann_at_uswest.net> wrote in message news:jIxo8.151$pV.127451_at_news.uswest.net... >
> In regards to shivers down your spine when others reference a primay key
in
> association with an entity, I defer to section 2.3.1, entitled Primary
Keys,
> in Peter Chen's, "The Entity-Relationship Model -- Toward a Unified Model
of
> Data."

A fine reference indeed. :-) But note the sentence just before this section: "In the following, we shall describe how to represent entities and relationships." Note the word "represent". What he is actually doing in section 2.3 Information Structure (level 2) is showing you how entity sets and relationships can be represented as tables. In other words, he is showing you how to map the whole thing to the relational model. Not really surprising then that he needs the term "primary key", is it? :-) He then goes on to explain the representation and indeed (to my great sadness) does not make much distinction between the entity sets and how they are represented as relations. This is not completely correct because when choosing a primary key you are making a small implementation decision, and that has no place in something called the conceptual model.

• Jan Hidders