Re: Defining proper relationships between similar entities

YP wrote:

> Consider a scenario in which various users must be stored in a
> relational database. Said users have different access levels. In
> addition, each type of user has different information associated with
> their account. Here's an example:
>
> Customer
> {
> Username
> Password
> FirstName
> LastName
> Address
> PhoneNumber
> EmailAddress
> }
>
> SupportPerson
> {
> Username
> Password
> FirstName
> LastName
> PhoneNumber
> }
>
> Administrator
> {
> Username
> Password
> EmailAddress
> }
>
> Based on business requirements, all of these users have a logon
> (username/password pair) in common, and some have a first/last name in
> common as well. Generally speaking, I find that this sort of asymmetry
> amongst related entities tends to surface rather frequently. My initial
> thought was to have a single denormalized table to represent all
> possible user types, but there are cases in which there is so great a
> difference in the amount of fields each entity has, it just seems wrong
> to have all those empty spaces. It would be nice to hear from some
> professionals on how this is handled as I'd like to avoid passing on
> the burden of maintaining a poorly designed database.

Read Fabian Pascal's _Practical Issues...._ book. Received on Mon Jan 22 2007 - 15:47:05 CET