Re: How to enforce subtypes/supertypes in Access 2000?

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" <nospam@xxxxxxxxxxx> wrote in message
news:bCnBg.220675$mF2.29695@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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" <fakeemail@xxxxxxxxx> wrote in message
news:44d5b441$0$21304$5a62ac22@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi folks,

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

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






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Relevant Pages

  • Re: How to enforce subtypes/supertypes in Access 2000?
    ... created a new unique multifield index based on ContactID and ContactTypeID ... ContactTypeID fields between tblContacts and tblIndividuals. ... and tblOrganisations in the same way. ...
    (microsoft.public.access.tablesdbdesign)
  • Re: How to enforce subtypes/supertypes in Access 2000?
    ... As to the use of table-level constraints, how do I set this up? ... two FK fields in tblContacts - one for IndivID and one for OrgID, ... ContactID the PK in both those tables. ... IndivID ...
    (microsoft.public.access.tablesdbdesign)
  • Re: How to enforce subtypes/supertypes in Access 2000?
    ... two FK fields in tblContacts - one for IndivID and one for OrgID, ... ContactID the PK in both those tables. ... IndivID ... ContactID (pk - autonumber) ...
    (microsoft.public.access.tablesdbdesign)
  • Re: How to enforce subtypes/supertypes in Access 2000?
    ... tblFiles - which, amongst other things, has the following three fields: ... essentially says that on client may be related to many files, ... tblContacts and tblClients? ... ContactID ...
    (microsoft.public.access.tablesdbdesign)
  • Re: How to enforce subtypes/supertypes in Access 2000?
    ... two FK fields in tblContacts - one for IndivID and one for OrgID, ... ContactID the PK in both those tables. ... IndivID ... The table tblIndividuals ...
    (microsoft.public.access.tablesdbdesign)
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