Re: Three table database - period (?)

In article <956s24$3vb$1_at_news.tue.nl>,   hidders_at_win.tue.nl (Jan Hidders) wrote:
> Jens wrote:
> > Hi
> >
> > I have been wondering about the merits / pitfalls of the
> > following table structure:
> >
> > Entity(ID)
> >
> > EntityAttribute(EntityID, AttributeID)
> >
> > Attribute(ID, Type, EntityID, Number, String, Date, Blob,
> > ...)
> >
> > This describes an entity that has some attributes linked to
> > it through the EntityAttribute table. The attribute table's
> > Type field describes which of the attribute fields is
> > actually used.
> >
> > I don't seem to need any more tables as I can describe
> > anything with these three (or can I?). I'm also concerned
> > about speed and space consumption but the flexibility this
> > seems to give me is tempting.
>
> The drawbacks are indeed the
> speed (more joins neccessary, constraint checking is going to be a lot
> harder and will more often require joins) and space (lots of extra IDs
> in lots of places)

Performance implications are probably much more severe than just more joins. In traditional schema, for example, I could create composite key index -- what do I do in metamodel?

Sent via Deja.com
http://www.deja.com/ Received on Tue Jan 30 2001 - 19:57:43 CET