Re: Square pegs in round holes

From: Graham Bellamy <>
Date: Thu, 23 May 2002 05:46:01 +1000
Message-ID: <acgvs2$fm2$>

"Mikito Harakiri" <> wrote in message

> > > Type Thickness(mm) Ratio(Sqm*mm/L) ContainerSize(L) TotalVolume(L)
> > > Cost($/L)
> > > Primer 1 0.99 20 40
> > > 0.50
> >
> > I don't understand how your (Sqm*mm/L) is functioning.
> > My Sq.m/L/mm is Square Meters per Litre for every 1mm thickness laid down.
> If you spill 1L of water into the area of 1 Sq.m what the depth of the
> pool would be?

I understand this concept, being that 1L=1000cubic cm. It was just the way you wrote the units down, I found it hard to imagine. Don't worry, I think I know what you're talking about.

> Identity 1/1/mm == 1mm is the other way to see that your Sq.m/L/mm
> unit must be the same as mine Sqm*mm/L. Now, obviously, 1 Sqm*mm= 1 L,
> so that the units we are considering is in fact just some factor. Let
> me know if your Sq.m/L/mm value could ever be greater than one.

I've seen the user enter 5 Sq.m/L of Primer. So either they're spreading it 5mm thick, or they're using a concentrate and mixing it with something (eg water), which would make it look like it covers 5Sq.m per L (at 1mm thick). I'll have to ask.

Also sand can be added to the Resin to make it go further. In which case, while the mix is still 1 L/Sq.m/mm, this could be comprised of 0.8L Sand and 0.2L Resin, or 1.25 Sq.m/L and 5 Sq.m/L respectively.

Or they could sprinkle a little bit of sand over the surface to make it non-skid, so they would look at this as covering 10 Sq.m per L (or probably kg, but lets not confuse this more) of sand used. So in your model, if the Rate is (say) 1, then the thickness would have to be stored as 0.1mm. Now the user must be allowed to enter an application rate of 10, and would want to see 10 Sq.m/L on a report and not see any thickness, as this would confuse him. So I need a way of storing what the input units are, and coming to a conclusion on whether the thickness needs to be shown etc.

Oh my god. Has anyone out there had this sort of trouble? This was supposed to be such a simple little db.

> > In the entry form, would it be advisable to base it on a query that calculates the
> > value, eventhough it won't be showing it on that form, such that any future queries
> > pluck that field out at will?
> I dont understand the last sentence.

Don't worry, I don't think it was such a smart question. It doesn't matter at what point the queries are created.


Graham Received on Wed May 22 2002 - 21:46:01 CEST

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