Re: Database theory and money

From: Alan <alanshein_at_spambuster.erols.com>
Date: Mon, 11 Sep 2000 09:21:32 -0400
Message-ID: <8pimf7$jei$1_at_bob.news.rcn.net>


In that case, use two columns, one for the amount, and one for the currency type.

"Chad" <cthomas500_at_home.com> wrote in message news:0D3v5.29946$E_6.11742167_at_news3.rdc1.on.home.com...
> Thanks for the feedback. I am familiar with Date's book. This just
 happens
> to be the first system where I have had to deal with multiple currencies.
> I'm looking for a good reference on this topic.
>
> For the record, I would allways store the currency indicator, but never in
> the same column. This particular system does not need to compare values
 in
> this column against other values in this column.
>
> Chad Thomas
>
> "Jan Hidders" <hidders_at_REMOVE.THIS.win.tue.nl> wrote in message
> news:8pibtr$qf4$1_at_news.tue.nl...
> > Chad wrote:
> > > I just want some feedback on storing monetary values of different
> > > currencies in the same column in a table. I think it violates
 relational
> > > principles.
> > >
> > > Does anyone have a good source on this?
> >
> > Look at "An Introduction to Database Systems" by C.J. Date. One
 principle
 is
> > that every column contains only values from a certain domain. Such a
 domain
> > is a set of (atomic) values with a specific meaning. So the domains
 'weight'
> > and 'height' may contain the same values but still are different
 domains.
 An
> > important property of values within a domain is that it must make sense
 to
> > ask if they are equal or not. For example, it usually does not make
 sense
> > to ask if weight X is equal to height Y, so these should be different
> > domains and therefore never in the same column.
> >
> > Whether this is the case in your table depends on what you exactly store
 in
> > the column. If it is just a number and the monetary unit is not
 indicated
> > anywhere then you probably have a problem anyway. If the monetary unit
 is
> > indicated somehow in another column then this may or may not violate the
> > principle mentioned depending upon whether you think it makes sense to
> > compare numbers of liras to numbers of dollars et cetera. (I think it
 does,
> > so as far as I am concerned you are not violating the principle.) If the
> > monetary unit is indicated in the same column then you are violating the
> > principle that values in columns should be atomic, i.e., cannot be split
> > into meaningful parts. But this latter principle is usually not
 considered
> > very important anyway (ususally a date is represented in one column
 although
> > by this principle it should be split).
> >
> > --
> > Kind regards
> >
> > Jan Hidders
>
>
Received on Mon Sep 11 2000 - 15:21:32 CEST

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