Updating a field in the table that is not part of the form

[Guest]

I have a form, that contains most of the fields in a table. I derive the
contents of one of the table fields (not on the form) as the user steps
through the form. What is the best way of updating the associated table with
the derived field value?, and where is the appropriate place to do that
function (pre-update of record)?

Hope that makes sense?

 

[John Vinson]

What is the best way of updating the associated table with
the derived field value?,

The best way is to not do so at all.

Storing derived data such as this in your table accomplishes
three things: it wastes disk space; it wastes time (almost
any calculation will be MUCH faster than a disk fetch); and
most importantly, it risks data corruption. If one of the
underlying fields is subsequently edited, you will have data
in your table WHICH IS WRONG, and no automatic way to detect
that fact.

Just redo the calculation whenever you need it, either as a
calculated field in a Query or just as you're now doing it -
in the control source of a Form or a Report textbox.

and where is the appropriate place to do that
function (pre-update of record)?

If you MUST store it, use VBA code in the Form's BeforeUpdate event:

Me!RedundantDerivedField = <expression>

John W. Vinson[MVP]

 

[Guest]

Thanks John.

As I'm new at this, I'm always looking for the best/proper way to do things.