Re: Noob needs polymorphism


"kj" <socyl@xxxxxxxxxxxxxxxxx> wrote in message
news:dea2go$7vj$1@xxxxxxxxxxxxxxxxxxxx
> In <1124630094.434037.22860@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> "--CELKO--"
<jcelko212@xxxxxxxxxxxxx> writes:
>
> >Don't use an RDBMS. This design flaw is called EAV
> >(Entity-Atrribute-Value) in RDBMS;
>
> Thanks, this is very helpful.
>
> I'm having a surprisingly difficult time finding a good
> description/analysis/critique of EAV online. I get a lot of Google
> hits, but none of the sites I visited seemed particularly useful.
> (I'm looking something not only for myself, but also to point other
> members of my team to. It will be a challenge for me to convince
> them that we should abandon the RDBMS strategy.)
>
> Also, my RDBMS textbook (Elmasri & Navathe, 3d ed) does not make
> mention of EAV. (I figure that if anyone is going to analyze EAV
> and tear it to bits if necessary, it would be EJ Data, but I'm away
> from my copy of his book ATM, so I have not checked it yet.)
>
> Do you by any chance know of a book or journal article that discusses
> EAV at length, and explains why it is a "flaw"? (Incidentally,
> FWIW, many of the pages on EAV that I found through Google advance
> it as a good thing...)
>
> kj
>
> --
> NOTE: In my address everything before the first period is backwards;
> and the last period, and everything after it, should be discarded.

It is like anything else; if you have too much flexibility it becomes
unwieldy. RDBMSs are more designed for stricter entity attribute
definitions. They are real work horses for that. For what you want to do I
don't think most RDBMSs are really designed for what you want to do. You
are going to have a lot of difficulties querying data and performance
problems. Look for something better designed for your problem. Too often
in the business world we see EAV used as a means of sloppy design - ultimate
flexibility, but very difficult to query and scalability problems.
Jim


.

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    ... >Don't use an RDBMS. ... This design flaw is called EAV ... In my address everything before the first period is backwards; ...
    (comp.databases)