Re: Calculated Fields in Postgres?

This is not a JDBC question, that's a basic SQL question, but any
way... You have some choices:

1- Use a view to show the data from the table plus the calculated fields.
2- Use a trigger to define the value of the calculated field on INSERT.

Which one you use depends on the usage scenario, basically how a
change of the mfg policy would affect you.  However, you seem to have
a problem with your table structure, so you should probably read a
little bit about normalization.  For example, it might make more sense
to convert everything to days, and forget about the 'Life Units'
field.

On 1/2/07, Jeanna Geier <jgeier@apt-cafm.com> wrote:
> Hello List!
>
> Still trying to learn Postgres... =)  I have a question on how/where to
> define a calculated field in a table...
>
> Let's say I have a 'Replacement Cost' table with the following fields:
>
> Original Cost
> Original Date
> Life Expectancy
> Life Units
>
> and I want to add a 'Mfg. Replace Date' field, which is a calculated field
> with the following formula:
>
> IF ('Life Units' = NAV)
>  THEN (NAV)
> ELSE
>  ( IF ('Life Units' = 'Day(s)'')
>      THEN (AddDate('Original Date,0,0,'Life Expectancy'))
> ELSE
>  ( IF 'Life Units'  = 'Month(s)'')
>      THEN (AddDate('Original Date',0,'Life Expectancy',0))
> ELSE
>   ( IF 'Life Units' = 'Year(s)'')
>      THEN (AddDate('Original Date','Life Expectancy',0.0))
> ELSE
> (today))))
>
> --------------------------------------------------------
>
> How/where do I define this calculated field?
>
> Any help or guidance that anyone could provide will be greatly appreciated!
>
> If any more information is necessary from my end, please let me know.
>
> Thanks,
> -Jeanna
>
>
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