Re: schema help

From: Cimode <>
Date: Wed, 26 Dec 2007 00:39:54 -0800 (PST)
Message-ID: <>

On Dec 25, 10:40 pm, Rob <> wrote:
> On Dec 25, 12:37 pm, magawake <> wrote:> Hello:
> > I am trying to learn SQL and RDBMS theories. To acheive this, I
> > decided to assign myself a project.
> > My project is basically, account for my NFS mounts, and keep track of
> > them. I want to see which filesystems are growing, and which
> > filesystems are staying the same. I will get an inventory daily. I
> > will grab the data and place it into a database, using PERL or AWK.
> [some illustrative data]
> > So my intentention is, to show do stats on these filesystems, and see
> > when it grows and when it stays the same. I will get these stats
> > daily, and hopefully in a month, I can see what is growing, shrinking,
> > and staying the same.
> > Any ideas on the schema? do I really need a RDBMS for this?
> > TIA
> A fascinating question I've long pondered. Since I am interested in
> the general question, I'll take the liberty to restate it, accurately
> I hope:
> Since a relational database represents the model state of a known
> universe, is it possible to ask/answer the question: How has the
> database changed over time?

Question: what is a *model state of a known universe*?

> Snodgrass advocates adding begin/end time attributes, for the data
> entry window and the data validity window (with representations for
> minus- and plus infinity). But am I really modeling change-over-time
> or just adding timeframes to snapshots? (Like using a timed exposure
> to take a picture with a camera when there's too little light.)
What does databases have to do with pictures?

> Would it not be better to utilize the OP's data capture approach by
> periodically evaluating a query, saving the query response externally
> and computing "deltas" between query responses (extensions) over
> time?? (This is fundamentally the data warehouse approach in which a
> relational database is used to capture periodic snapshots.)
> What do other people think about this? Is it better to implement a
> temporal database or to capture snapshots of a non-temporal database
> (externally or in a data warehouse) and compute the changes?
What is a *temporal database*?
> Rob
Received on Wed Dec 26 2007 - 09:39:54 CET

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