[AccessD] Lookup Fields in Table Design

Hi Gustav:
"moot" would be the correct word - if it really applied ;o)

I actually do things the way you describe. But I do it based on other
developers advice that I never really questioned before.

I believe the discussion is: why not (use the lookups property)?

For instance, when I did use it on a particular project where it fit the
need it did make form design quicker and easier (once I adjusted to it). It
makes placing combo boxes (in my case to lookup a foreign key) very simple.
Just drag the control out and forget about it. A one step process.

Being suspicious that it would cause problems later I went back to how I had
done it previously. The 2 or 3 extra steps when placing a combo box really
isn't adding a lot of overhead to my overall development time.

But it does beg the question: why not?

John B.

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com]On Behalf Of Gustav Brock
Sent: Friday, March 26, 2004 11:04 AM
To: Access Developers discussion and problem solving
Subject: Re: [AccessD] Lookup Fields in Table Design


Hi all lookuppers

Maybe I'm dense but - as mentioned by Ken - if you really need the
feature of lookup fields (and I did once for some superuser
administrative tasks performed once a year or never, thus not
justifying design of eight forms) you simply - in a separate frontend
database - create some queries retrieving exactly the fields you need
(which excludes the ID), readable aliases for the fields, and lookups
as needed.

Then everybody is happy. You avoid fiddling with the table design and
you can easily redesign the queries if and when needed and you take
advantage of a feature of Access which can be handy.

And this discussion becomes moot (isn't that the wording for such a
situation you use "over there"?)

/gustav


> Here are "The Evils of Lookup Fields in Tables" from Dev's website:

> A Lookup field in a table displays the looked-up value. For instance, if a
> user opens a table datasheet and sees a column of company names, what is
in
> the table is, in fact, a numeric CompanyID, and the table is linked with a
> select statement to the company table by that ID.

> Any query that uses that lookup field to sort by that company name won't
> work. Nor will a query that uses a company name in that field as a
criteria.
> If a user creates a combobox to select the company using a value list, the
> data in the table can be over-written.

> Another relationship is created which then creates another set of indexes
> when a Lookup field is created, thus bloating the database unnecessarily.

> If a combobox based on the lookup is used in a form, and a filter is
> applied, the persistent filter effect of Access often saves the filter and
> the next time the form is opened, there will be a prompt for the value
> (which cannot be provided, thus creating an error).

> Reports based on the lookup field need a combobox to display the data,
> causing them to run more slowly. The underlying recordsource can also be
> modified to include the table, however the index, (unless it was set up
> within a proper relationship) may not be optimized.

> Lookup fields mask what is really happening, and hide good relational
> methodology from the user.

> The database cannot be properly upsized to, or queried by, another engine
> (without removing all the lookup fields) because no other engines use or
> understand them.

> If security is implemented, permissions to tables is usually denied, and
> RWOP queries are used for data access. There will often be errors that
there
> are no permissions on a specific table that isn't even being used in a
query
> (because the lookup field is). If the queries are nested or complex, it
can
> take some time to track down the lookup that's causing the error (that is,
> if it occurs to you).

> http://www.mvps.org/access/tencommandments.htm

--
_______________________________________________
AccessD mailing list
AccessD at databaseadvisors.com
http://databaseadvisors.com/mailman/listinfo/accessd
Website: http://www.databaseadvisors.com