Re: SQL

In article <1138127666.875967.222550@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
frebe <fredrik_bertilsson@xxxxxxxxxxx> wrote:
>> If we ignore the persistence aspect, what remains is the organization of
>> data according to the relational model. That's certainly useful, but it's
>> not 'MANY' features.
>
>Here are my top four non-persistence related features that I use every
>day. I think they are very important.
>* Queries.

Those I'd generally consider to be part of the relational model - the
queries are how you access data, perform joins (which are part of the
relational model), etc.

>* Transactions.

Those are definitely useful, but are not specific to databases, neither
in general nor specifically relational ones.

>* Referential integrity

.... has to be maintained somehow: dangling references would be a problem
in any system. SQL can prevent you from putting the database into an
inconsistent state, true, but you still have to manually keep the
references up-to-date, just as in any other system.

>* Caching.

Caching also isn't specific to RDBMS:es. If you're using a modern OS, you
can hardly _avoid_ some level of caching these days, even if you're using
flat files!

So, all of these things you mention above are, in my view, either direct
consequences of the relational model, or features that are not specific to
relational databases (and could thus be available to you using a
non-relational system for storing and accessing data). Do you strongly
disagree?

>> Nevertheless, persistence is considered one of the cornerstones of
>> RDBMS:es, and one thing that RDBMS:es are expected to offer.
>Do do you have anything to back it up with?

Not really - only my general experience with databases, which I admit is
not _hugely_ extensive. I am willing to be corrected on this point :) Do
you have any examples of relational databases that have specific features
for non-persistent usage? All the relational databases I've looked at
(again, a limited number) appear to put a lot of weight on the persistence
aspect.

>> However, if you look around, I think you will see that the
>> _vast_ majority of uses of databases are, in fact, for _persistent_
>> storage of data.
>Only in the OO world. In the rest of the world there are many examples
>of the opposite.

I'm open to be educated on the subject - please, could you point me at
some examples?

[ In my experience, even when I was developing procedural systems, in
those systems, relational databases where used to work with persistent
data. Transient data was generally stored in bespoke data structures in
memory. This is without any OO involved. ]

>Fredrik Bertilsson
>http://butler.sourceforge.net

Best wishes,

// Christian Brunschen
.

Relevant Pages

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