On Apr 20, 2008, at 6:15 PM, Mr. Frank Cobia wrote:
I have a database design question. I am posting it to the WebObjects
list because I am building a WebObjects app and want a solution that
works well for EOF.
I have a table of data that has to have a location associated with
it. Unfortunately the level of the location is not constant. The
data can be associated with a Country, Region, State, Metro Area,
County or City. Each of those levels is its own table with
relationships pointing to the related locations. i.e. a State knows
which Region it belongs to and which Metro Areas belong to it.
I have been unable to come up with a design that seems elegant. I
have thought of having 6 separate relationships to each of the
location levels, but it seems to duplicate data and the data could
get out of sync if a state is moved to a different region or a City
is moved to a different county.
Has anyone had a situation like this and come up with a good solution?
This seems like a good place for inheritance with an abstract EO of
Location with concrete subclasses of Country, Region, State, Metro
Area, County or City. For some operations, having them in separate
tables might cause more fetches than you want. Using single table
inheritance would address that.
Chuck
--
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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