--- In IBObjects@y..., Helen Borrie <helebor@w...> wrote:
> At 06:27 AM 02-02-01 +0000, you wrote:
> >I am used to using Calculated fields with TTables. This worked
fine
> >with Paradox but obviously isn't the best way to use IB. I am now
> >converting any Calculated fields to Computed By fields. However
the
> >problem is that computed by fields are only computed when the table
> >is refreshed.
> >
> >Is there a more efficient way of forcing Computed By fields to
> >display other than issuing a Refresh? Or is there a better
solution?
>
> Well, you have to understand that in a client/server database, the
Computed
> By column is computed from the value stored in its definition.
What is
> wrong with a refresh? It's the way to do it with C/s.
>
> If you're using TIBOQuery, you can still create a calculated
field...
>
>
>
> >In addition, what is the best way to create a 'lookup' field. ie a
> >computed by field that gets its value from another table?
>
> Use a subselect in your query, viz.
>
> select OrderID, CustomerID,
> (select FirstName||' '||LastName from Customer where
> Order.CustomerID=Customer.CustomerID) AS CustomerName,
> Field3,
> Field4
> from Order
>
> Note that you will get an error if your subselect is capable
(through
> inter-table dependencies) of returning more than one row. And,
once again,
> you won't get the subselect field populated until you do a refresh.
>
> btw, this is only part of the story with native IBO lookups. If
you have
> the Getting Started Guide, read up the sections on Keysource-Lookup
> relationships and TIB_LookupCombo.
>
> Helen
>
>
>
> Helen
>
> All for Open and Open for All
> InterBase Developer Initiative · http://www.interbase2000.org
> _______________________________________________________