[AccessD] Programming

>I start by saying no in principle.

Precisely

>OTOH the reverse may, in many cases, be true, i.e. that if a calculation
changes existing records do want to be affected.

Precisely

>The other one time I go for YES is for speed.

Yes, with a BIG but...

If you are going to do this you must make sure you have a change flag that
tells you if any of the data has changed, necessitating a new calculation.

John W. Colby
www.ColbyConsulting.com 

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Andy Lacey
Sent: Friday, May 13, 2005 4:39 AM
To: Access Developers discussion and problem solving
Subject: Re: [AccessD] Programming


I start by saying no in principle. Then I look for exceptional
circumstances. You mention Client Charge. To me that sounds like a Yes
because the charging algorithm may change and if it does the new calculation
should not affect previous billings. So that's one argument for storing a
calculated value. OTOH the reverse may, in many cases, be true, i.e. that if
a calculation changes existing records do want to be affected. That would be
a sound argument for not storing those calculated values.

The other one time I go for YES is for speed. If you are likely to have to,
for example, select records where jobtotalhours>x then I'd certainly
consider storing it. At the end of the day the system's for the benefit of a
user. If you can improve the user's experience by giving him/her a quicker
answer, and the penalty isn't too great, then I'd store it. Just make damned
sure no-one can alter start or end without your program recalculating total
hours.

My 2 pen'orth Richard

--
Andy Lacey
http://www.minstersystems.co.uk



--------- Original Message --------
From: Access Developers discussion and problem solving
<accessd at databaseadvisors.com>
To: AccessD <accessd at databaseadvisors.com>
Subject: [AccessD] Programming
Date: 13/05/05 07:56

>
> Hi Group
>
> A general programming question.  Would you ever store calculated 
> values in a table.  My example is this...
>
> I have a Timesheetline table recording jobstart, jobend times/dates 
> etc. Do I store jobtotalhours in the table and do I store Client 
> charge and EmployeePaid amounts.  I would not normally store 
> calculated values in a table but as these calculations are quite 
> complex (different charge rates, time periods e.g std and overtime 
> etc) I thought that once calculated (at the point of data entry) why 
> not store these values in table (may improved report 
> speed/programming). Alternativley, isn't this what computers are for 
> ie carrying out complex calculations so why store value, when it comes to
reporting on or
> displaying etc simply recaculate.   My leaning now is not to store these
> values. Any thoughts?
>
> Richard
>
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>
>
>
>
>
>

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