hmm, okay. i don't know that i'd set up the tables quite that way, but
you've analyzed the business process and i haven't - so i also don't know
that any alternate suggestions i made would actually be "better", rather
than simply different, or even not as good.

so to get back to your original question: AFAIK, table constraints are user
in SQL server, and perhaps other database types; but are not available in
Access. so you'll need to enforce the business rule at the form level. in
the main form, you can set up some code on the combo box control's
BeforeUpdate event to check the "other" subtype table for a record
containing the current Contact record's primary key value (a simple DCount()
function would handle that easily). if it exists, you can either cancel the
control's BeforeUpdate event, with a message box to tell the user to delete
the current subform record before adding a record to the other subform - or
tell the user that if they choose the alternate value in the combo box, the
record in the current subform will be deleted, and asking them to choose to
continue or cancel. if they cancel, then just cancel the BeforeUpdate event;
if they continue, then automatically delete the current subform record, and
then switch to the other subform.

hth


"Bob" wrote in message
...
Thanks for your interest Tina,

My full table structure is as follows:

tblContacts:
ContactID (pk)
ContactType (fk)
Address1
Address2
City
State
PostCode
PostalAddress1
PostalAddress2
PostalCity
PostalState
PostalPostCode
Tel
Fax
Mob
Email

tblIndividuals:
IndivID (pk)
ContactID (fk)
Title
FirstName
MiddleNames
LastName
Suffix
EmployerID (fk) (links back to tblContacts.ContactID (1:Many))
EmpDirectPhn
EmpDirectFax
EmpEmail

tblOrganisations:
OrgID (pk)
ContactID (fk)
OrgName
TradingName
IsACompany (yes/no)
ACN (Australian Company Number)
ABN (Australian Business Number)
Website

tblContactType
ContactTypeID (pk)
ContactType ("Indiv" or "Org")

As you can see, tblContacts lists the location (ie residential or
business)
addresses, postal addresses and (residential or business)
telecommunication
details for all contacts. The table tblIndividuals segregates the
individual-specific biographical information together with the
individual's
work details. The EmployerID links back to the ContactID field in
tblContacts because we often end up acting for employees of existing
corporate clients or for muliple employees of non-client organisations. I
segregate the Organisation details so that I can record details for all
businesses (incorporated and unincorporated (ie sole-proprietorships,
partnerships, associations, churches etc)) that simply aren't relevant to
individuals. It also enables me to set up a separate table
(tblOrgContacts)
to identify individual contacts for the organisation entities (a 1:Many
relationship is established between the two tables based on
tblOrganisations.OrgID (pk) and tblOrgContacts.ContactID (fk)). For our
purposes, we do not require any contacts to be linked with Individuals as
opposed to Organisations.

The above tables essentially constitute the whole set of "contacts" for my
employer's business; tblContacts is then linked with tblClients which
identifies those contacts that are in fact clients:

tlbClients:
ClientID (pk) (autonumber)
ContactID (fk) (related to tblContacts.ContactID) (1:1 relationship)
ReferrerID (fk) (related to tblContacts.ContactID) (1:Many relationship)


Regards
Bob


"tina" wrote in message
...
my first thought is: do you really need to to separate the individuals
records and organizations records into different tables? suggest you
post
all the fields in each of those two tables so we can review them;
perhaps
we
can help you combine the two tables into one, with the addition of a
single
field specifying either "individual" or "organization".

hth


"Bob" wrote in message
...
Hi folks,

I am creating a client database in MS Access with the following
(simplified)
table structu

tblContacts:
ContactID (pk - autonumber)
ContactType (fk) (from tblContactTypes)
ContactDetails (text)

tblIndividuals
IndivID (pk - autonumber)
ContactID (fk) (from tblContacts)
IndivDetails (txt)

tblOrganisations
OrgID (pk - autonumber)
ContactID (fk) (from tblContacts)
OrgDetails (txt)

tblContactTypes (serves as a lookup table)
tblContactTypeID (pk - autonumber)
tblContactType (txt - contains values "Indiv" or "Org")

There is a 1:1 relationship between the ContactID (pk) in tblContacts
and
the ContactID (fks) in tblIndividuals and tbleOrganisations.

I have created a form in MS Access for entering client details. At the
moment, I have two subforms - frmIndiv and frmOrg - which are
positioned
on
my main entry form.

The form contains a combo-box from which the user can select "Indiv" or
"Org" as the ContactType. Depending on the value in the combo-box, one
or
other of the two subforms will become visible.

At the moment, the user selects - say - "Indiv" as the ContactType and
proceeds to enter details for this type of Contact. When this happens,
the
ContactID for the current record in tblContacts table is mirrored in
the
ContactID foreign key in the tblIndividuals table. This is what I want.

The problem is that once the user is finished (and whilst still in the
same
record in the tblContacts table), the user can select "Org" from the
combo-box and be provided with a empty copy of the sub-form frmOrg. If
the
user proceeds to enter data on the sub-form, the ContactID foreign key
in
the frmOrg will also mirror the ContactID in tblContacts.

This results in a record in both of my subtype tables (tblIndividuals
and
tblOrganisations) having a record which points to the same ContactID in
the
supertype table (tblContacts).

How can I prevent this from happening? - ie make sure that each record
in
the subtype tables points to a record in the supertype table for which
no
subtype record has already been created? (That's a mouthful - I hope it
makes sense). I've seen some references to "check constraints" on the
internet which I believe might help achieve my objective. But - so far
as
I
am aware - I can't impose check constraints on fields in Access 2000.
(I
have seen a suggestion that this might be achieved by using ADO, but no
code
example was given).

Any pointers would be appreciated.

Please note, I am a complete novice at this.


TIA
Bob