[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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