Marnen Laibow-Koser wrote:
Will Merrell wrote:
Taylor Strait wrote:
I am trying to decide between two different database architectures for
an application to manage properties. For capturing the property
features, I have two options: a single model/table with all the features
as fields, or a set of joined models - property, feature, feature data.
(see attached ERD diagram)
You're right that option A is pretty much a bad idea. I can't tell you
how much time I have spent refactoring databases that were *guaranteed*
never to change.
That shouldn't be a problem. Broadly speaking, it is better to refactor
a database tomorrow than to overdesign it today.
I'm certainly not in favor of over design, which is why I suggested
something in between. That said, I have rarely seen a case where wide
and shallow is the proper solution. The OPs problem looks like it needs
some kind of normalization.
In that sense option B is much better.
However, there may be a solution between the two.
Consider the following table:
Features
id
name (the name of the feature: 'pool', 'doorman', or whatever)
featureable_type ('property', 'unit', or 'room')
featureable_id (property.id, unit.id, or room.id)
With this, you just add whatever feature you want. If the record exists
the property has the feature. The name field can be user enterable, or
you can fill it from a listbox if you want to control what the user can
enter. The list can even be editable by an admin if you want the control
and the extensibility.
That's terrible! It defeats the point of having a database. Don't ever
do that unless there's absolutely no alternative.
Could you say a little more about which part of this you find terrible.
I have used techniques like this for some situations, and have seen
others use it also. If I'm missing something I want to know. If I
misspoke, I want to clean it up.
-- Will
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