How to enforce subtypes/supertypes in Access 2000?
Bob
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
tina
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" <fake...@yahoo.com> wrote in message
news:44d5b441$0$21304$5a62...@per-qv1-newsreader-01.iinet.net.au...
Bob
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" <nos...@address.com> wrote in message
news:bCnBg.220675$mF2....@bgtnsc04-news.ops.worldnet.att.net...
tina
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" <fake...@yahoo.com> wrote in message
news:44d6238f$0$21313$5a62...@per-qv1-newsreader-01.iinet.net.au...
tina
option in the main form's combo box control, then use VBA to set the
subform's SourceObject, LinkChildFields, and LinkMasterFields properties for
the appropriate subform object. going from memory, you may need to put a
[SubformControlName].Form.Requery command at the end of the code, so that
the correct records will populate the chosen subform.
hth
"tina" <nos...@address.com> wrote in message
news:1oqBg.221099$mF2.2...@bgtnsc04-news.ops.worldnet.att.net...
Bob
I'll give that go.
Regards
Bob
"tina" <nos...@address.com> wrote in message
news:5VqBg.221185$mF2....@bgtnsc04-news.ops.worldnet.att.net...
Bob
I did have a few extra questions.
Firstly, in what way might you have otherwise structured the relevant
contact information? I'm a novice, so I'm open to ideas.
Secondly, without complicating things too much, I should mention that my
table structure includes two additional tables:
tblClientFiles - a junction table with ClientID and FileID specified as the
primary key; and
tblFiles - which, amongst other things, has the following three fields:
FileID (pk - autonumber) (with a 1:Many relationship with tblClients.FileID)
FileNumber (txt - alphanumeric content (needs to be changed from time to
time, so not used as pk)
DateOpened - date/time
DateCompleted - date/time
To be honest, I struggle with insert/update commmands at the best of times.
It seems even more complicated once you start normalising and multiplying
the tables.
Anyway, my queries are:
(a) based on the table structure I have outlined, how would you construct
the sql strings to select, insert and delete a record into tblFiles?; and
(b) how would you construct the same strings where the "client" consists of
two persons (say a husband and a wife) who each have their own record in
tblContacts and tblClients?
By the way, someone else was pretty much asking the same question I asked at
the outset (about ensuring that only one of the subtype tables was updated)
- see http://www.dbforums.com/archive/index.php/t-1053752.html. One of the
responses to that post was as follows:
Because you do not specify what is in the "generic table" [equivalent to my
tblContacts], it is difficult
to offer specific suggestions. I can suggest that in the generic table, you
identify the type of contact [equivalent to my tblContactType], create your
query linking to both, and use an
outer join in order to allow one of the related tables to return a Null
entry. By outer join, I mean rightclicking on the join line between the data
sources in the Query, and choosing "All records from Contacts [ie my
tblContacts] and only those
that match from People [ie my tblIndividuals]" and "All records from
Contacts and only those that
match from Companies [ie my tblOrganisations]".
I don't quite understand what this means. Does it mean that in order to
perform select/insert/update commands programatically on, say, tblFiles or
tblOrganisations, I will need to do a whole lot of "outer joins"? If so,
what would one look like in my case?
Regard
Bob
"Bob" <fake...@yahoo.com> wrote in message
news:44d65939$0$21282$5a62...@per-qv1-newsreader-01.iinet.net.au...
tina
"Bob" <fake...@yahoo.com> wrote in message
news:44d666e6$0$21306$5a62...@per-qv1-newsreader-01.iinet.net.au...
> Tina,
>
> I did have a few extra questions.
>
> Firstly, in what way might you have otherwise structured the relevant
> contact information? I'm a novice, so I'm open to ideas.
sorry, didn't mean to be a tease. as i said, since i haven't analyzed the
business process, i couldn't state an alternate tables/relationships design
with confidence. i tend to stay very much "inside the box" on
table/relationship design, and have trouble with the more unusual
configurations that are necessary to model some real-world relationships. i
wish we could get Tim Ferguson into this thread; he's about the best i've
seen in these newsgroups re solving non-standard relationships and
explaining the configurations in a way that is easy to understand.
>
> Secondly, without complicating things too much, I should mention that my
> table structure includes two additional tables:
>
> tblClientFiles - a junction table with ClientID and FileID specified as
the
> primary key; and
>
> tblFiles - which, amongst other things, has the following three fields:
> FileID (pk - autonumber) (with a 1:Many relationship with
tblClients.FileID)
> FileNumber (txt - alphanumeric content (needs to be changed from time to
> time, so not used as pk)
> DateOpened - date/time
> DateCompleted - date/time
hmm, i do have to wonder here about your relationships. if tblFiles is
related to tblClients via a junction table called tblClientFiles, then why
is tblFiles also directly linked to tblClients? use of a junction table
essentially says that on client may be related to many files, and one file
may be related to many clients - a many-to-many relationship that the
junction table resolves into two one-to-many relationships. but a direct
relationship says that one client may be related to many files, but each
file is related to only one client - which is a straightforward one-to-many
relationship. so we have an apparent contradiction here.
sorry, hon, the above is all way too theoretical for me; i'm very much a
nuts-and-bolts person. if you can lay out a specific scenario, explaining
what the setup is and what you're trying to do in this situation, i'll work
on a solution with you. in any event, i can't help at all until we iron out
the issue of the real-world relationship between tblFiles and tblClients.
hth
Graham Mandeno
PMFJI :-)
In a Jet (Access) database, there is no way to enforce this sort of entity
subclassing at the engine level. The only way to do that would be to have
two FK fields in tblContacts - one for IndivID and one for OrgID, and have a
table-level constraint (validation rule) to specify that they cannot both be
Null.
Using the structure you have, you can go most of the way there using a
BeforeUpdate event procedure on your ContactType control.
Something like this (pseudo-code):
If ContactType.OldValue isn't null then
lookup corresponding record in table corresponding to OldValue
If record exists then
Heavy warning message about changing contact type
If user wishes to continue then
delete old related record
else
cancel = True
End If
End If
End If
BTW, I think you are complicating matters by having separate (AutoNumber?)
PKs in your Individuals and Organisations tables. I suggest you make
ContactID the PK in both those tables.
--
Good Luck!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <fake...@yahoo.com> wrote in message
news:44d6238f$0$21313$5a62...@per-qv1-newsreader-01.iinet.net.au...
Bob
Re the relationship between tblFiles and tblClientFiles, I think I got
carried away. There is no link between tblFiles and tblClients. The
tblFiles.FileID has a 1:Many relationship with tblClientFiles.FileID.
Sorry about that.
The real-world scenario I have is this:
The database is for a small accounting firm.
The firm opens one file per new matter. Each time a new file is
opened, the following details are recorded about the file:
(a) the file's number;
(b) the date the file is opened;
(c) the client's name, and various contact details (ie all known
addresses, telephone numbers and email addresses) - the client can be a
single private individual, or a couple; or an organisation
(company/partnership/association).
(d) a one or two line description of the matter - eg tax returns for
2005-2006.
As the file progresses, it is usually the case that a number of
contacts specifically for that file might develop (eg a specific person
at the tax office). The same contact might not apply to other files.
I call these file-specific third-party contacts.
There will usually be a number of contacts that relate specifically to
the client - eg the director of a corporate client. I call these
client-specific contacts.
There will also be third-party contacts with whom the firm liaises on
various files - eg a particular supervisor for a specific section in
the tax office. I call these generic third-party contacts.
I want to do the following:
(a) record each new contact as it is created - regardless of whether
the contact is a client, a file specific third-party contact, a
client-specific client-contact, or a generic third-party contact.
Hence my tblContacts, tblIndividuals and tblOrganisations tables.
(b) readily identify which contacts are clients, and by whom they were
referred. Hence, my tblClients table. The obvious rule here is that
an individual or organisation cannot be client unless they are already
a contact.
(c) create a record that links a particular client (or two clients in
the case of a spousal relationship) to a specific file (obviously the
same client(s) may have other files - hence why I have set up a
junction table between tblClients and tblFiles).
(d) record the required file details. Hence my tblFiles table.
(e) identify the client-specific contacts (hence my tblOrgContacts
table). The same contact can be a contact for more than one client (eg
where a person is the director of multiple companies). My ultimate
intention is to have this information displayed to the user on a form
each time they open a record in tblClients or tblFiles.
(f) finally, identify the file-specific and generic third-party
contacts. This information will also be displayed on a form each time
a record in tblFiles is opened.
My immediate aim is to ensure that anyone who wants to lookup the
contact details for a particular File or Client can do so by simply
opening a form linked to the relevant table and have all of the
information readily displayed for viewing, updating or deleting.
Now, when I create (insert) a record for a new File, what I **think** I
need to do is this:
(i) check if there is already a tblContact record for the Client - if
not, create one. Obviously, if a new contact record is created, I'm
going to need to grab the latest ContactID. Also, inserting a new
record would obviously involve:
(a) ensuring that there isn't already a record in either of the
"subtype" tables (Individuals or Organisations); and
(b) creating records in tblOrgContacts if necessary.
(ii) check if the Contact has already been identified as a client - if
not, create a record in tblClients;
(iii) create the new record in tblFiles; and
(iv) (finally?) create the new record(s) in tblClientFiles.
I assume that the update and delete processes will need to traverse
roughly the same procedure.
What I'm not clear on is:
(1) do I need a whole bunch of joins every time I insert and/or update
and/or delete a record in tblFiles (say)?; and
(2) how do I construct, say, an insert sql statement (for a new file)
that involves so many tables? Do I need to nest a whole bunch of select
statements somewhere; if so, how?
Thanks
Bob
Bob
Thanks for the tips. I'll re-examine the use of the autonumbers in the
two sub-tables.
As to the use of table-level constraints, how do I set this up? I
mean, I know I can specify that a particular field can't be null. But
how do I force a check on the null value of another field (field B)
before allowing one field (field A) to be null? Along the same lines,
how can I make sure that at least one field must be have a value?
I assume that this would ordinarily be achievable at the form level -
but you mention table-level constraints. I'm all ears :-)
Going off topic a bit, where the form is concerned I've noticed that my
database saves data automatically even if I close the form within
pressing save on the toolbar. I assume there is some kind of auto-save
when you enter data into a form - but this does not always happen.
Sometimes it saves, sometimes it doesn't. How do I force a prompt to
save every time the form closes? (I located some example code - which
I don't have handy - but it does not seem to work).
TIA
Bob
Bob
Nevermind my last post re the table-level constraints. I just re-read
yours: BeforeUpdate event - got it. I'm a bit slow today. :-D
I'm still interested re the save prompt question though.
Regards
Bob
Jamie Collins
Graham Mandeno wrote:
> In a Jet (Access) database, there is no way to enforce this sort of entity
> subclassing at the engine level. The only way to do that would be to have
> two FK fields in tblContacts - one for IndivID and one for OrgID, and have a
> table-level constraint (validation rule) to specify that they cannot both be
> Null.
That's got to be a misstatement!
The standard approach to implementing such subclass is to have a
superclass for both individuals and organizations; this can certainly
be implemented in Jet using referential integrity. If there are only
two types, each of which needs a base table in the schema, a
ContactTypes table is overkill:
[I'm avoiding PRIMARY KEY in favour of NOT NULL UNIQUE because
clustering on disk is OT; syntax requires ANSI query mode in the Access
UI or an OLE DB (e.g. ADO) connection.]
CREATE TABLE LegalPersons (
legal_person_ID INTEGER NOT NULL UNIQUE,
legal_person_type VARCHAR(5) NOT NULL,
CHECK (legal_person_type IN ('Indiv', 'org')),
UNIQUE (legal_person_type, legal_person_ID)
);
CREATE TABLE Individuals (
legal_person_ID INTEGER NOT NULL UNIQUE,
legal_person_type VARCHAR(5) NOT NULL,
CHECK (legal_person_type = 'Indiv'),
UNIQUE (legal_person_type, legal_person_ID),
FOREIGN KEY (legal_person_type, legal_person_ID)
REFERENCES LegalPersons (legal_person_type, legal_person_ID),
last_name VARCHAR(35) NOT NULL...
);
CREATE TABLE Organizations (
legal_person_ID INTEGER NOT NULL UNIQUE,
legal_person_type VARCHAR(5) NOT NULL,
CHECK (legal_person_type = 'Org'),
UNIQUE (legal_person_type, legal_person_ID),
FOREIGN KEY (legal_person_type, legal_person_ID)
REFERENCES LegalPersons (legal_person_type, legal_person_ID),
trading_name NVARCHAR(255) NOT NULL...
);
CREATE TABLE Contacts (
legal_person_ID INTEGER NOT NULL,
legal_person_type VARCHAR(5) NOT NULL,
FOREIGN KEY (legal_person_type, legal_person_ID)
REFERENCES LegalPersons (legal_person_type, legal_person_ID),
address_line_1 VARCHAR(30) NOT NULL...
<<needs a key>>
);
OK, I know what you are thinking: how to prevent a contact being
created for a row in LegalPersons that does not exist in either
Individuals or Organizations?
Something like this:
CHECK (1 = (SELECT IIF(Contacts.legal_person_type = 'Org', 1, COUNT(*))
FROM Individuals
WHERE Individuals.legal_person_ID = Contacts.legal_person_ID)
),
CHECK (1 = (SELECT IIF(Contacts.legal_person_type = 'Indiv', 1,
COUNT(*))
FROM Organizations
WHERE Organizations.legal_person_ID = Contacts.legal_person_ID)
),
...
Even you implied structure (i.e. omitting the LegalPerson table), you
*can* implement the foreign keys in Jet: using the same CHECKs as
above:
CREATE TABLE Individuals (
individual_ID INTEGER NOT NULL UNIQUE,
last_name VARCHAR(35) NOT NULL...
);
CREATE TABLE Organizations (
organization_ID INTEGER NOT NULL UNIQUE,
trading_name NVARCHAR(255) NOT NULL...
);
CREATE TABLE Contacts (
legal_person_ID INTEGER NOT NULL,
legal_person_type VARCHAR(5) NOT NULL,
CHECK (legal_person_type IN ('Indiv', 'org')),
CHECK (1 = (SELECT IIF(Contacts.legal_person_type = 'Org', 1, COUNT(*))
FROM Individuals
WHERE Individuals.individual_ID = Contacts.legal_person_ID)
),
CHECK (1 = (SELECT IIF(Contacts.legal_person_type = 'Indiv', 1,
COUNT(*))
FROM Organizations
WHERE Organizations.organization_ID = Contacts.legal_person_ID)
),
address_line_1 VARCHAR(30) NOT NULL...
<<needs a key>>
);
I would not recommend 'mixing' identifiers in this way. However, I
trust the above is sufficient for you to realize that it is possible to
enforce such constraints at the engine level in Jet.
Jamie.
--
Bob
How exactly do I switch to ANSI mode?
Regard
Bob
"Jamie Collins" <jamiec...@xsmail.com> wrote in message
news:1154946669....@n13g2000cwa.googlegroups.com...
Graham Mandeno
Yes, it was a misstatement - I meant to say "cannot both be NON-Null" :-)
Your solution involving duplicating the sub-type in the sub-tables and using
a two-field relationship is simple, elegant and brilliant. You say this is
"the standard approach" but I can't believe that I have never come across it
before, and it is so simple that I'm ashamed I never thought of it myself!
One question though - is there any reason not to put the "common" fields in
the superclass table? In other words, why not combine the Contacts and
LegalPersons tables?
--
Thanks!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Jamie Collins" <jamiec...@xsmail.com> wrote in message
news:1154946669....@n13g2000cwa.googlegroups.com...
>
Graham Mandeno
The solution that Jamie gave is simple and elegant. To translate it into
Access table design terms (which might be more familiar to you than ANSI-92
DDL statements!):
Add a unique index to tblContacts involving ContactID AND ContactType. Next
add a ContactType field to both tblIndividuals and tblOrganisations and for
each, set the default value to the corresponding contact type and set the
validation rule to =<contact type> and set required=Yes. (In other words, an
individual MUST be an individual and cannot be an organisation, and
vice-versa).
Now, add a 1:1 relationship with referential integrity between
ContactID/ContactType in tblContacts and tblIndividuals, and the same for
tblOrganisations.
Now the engine will look after the integrity for you. If a record in
tblContacts has a matching record in one of the other tables, then the
contact record can neither be deleted, nor changed to the other contact
type, unless the related subclass record is first deleted.
To answer your other questions:
1. A table-level validation rule can be created in the Table Properties
window (View>Properties in design view). For example:
([IndivID] Is Not Null) Xor ([OrgID] Is Not Null)
However, I would NOT use this two-field approach for your particular
problem.
2. You can force a prompt before saving a record using the form's
BeforeUpdate event.
Select case MsgBox("Save changes?", vbYesNoCancel)
case vbYes
' do nothing
case vbNo
Cancel = True
Me.Undo
case vbCancel
cancel = true
End Select
3. You can set ANSI-92 mode via Tools>Options>Tables/Queries. Use with
caution!
--
Good Luck!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <woodl...@yahoo.com> wrote in message
news:1154923513.2...@h48g2000cwc.googlegroups.com...
Jamie Collins
Graham Mandeno wrote:
> duplicating the sub-type in the sub-tables and using
> a two-field relationship is simple, elegant and brilliant. You say this is
> "the standard approach" but I can't believe that I have never come across it
> before, and it is so simple that I'm ashamed I never thought of it myself!
>
> One question though - is there any reason not to put the "common" fields in
> the superclass table?
Yes, the shared fields would be best in the superclass table. As I'm
sure you are aware, there is distinction between a shared attribute
(inheritance) and two attributes sharing a name (coincidence) e.g.
patient may have a legal name attribute and a medication may have a
legal name attribute but they do have a shared superclass.
> why not combine the Contacts and
> LegalPersons tables?
It's probably a 1:m relationship e.g. an organization may have more
than one contact. Also, an organization may have a contact that is an
individual who has a collection of contacts in the context of being a
contact for that organization as well as contacts in their own right
e.g. work, home (and they may have more than one home), etc. There is
certainly potential for the contacts to be a structure: each contact
type - postal, email, web, telephone, fax, etc - should have probably
be in a table of their own, with perhaps shared super classes (e.g.
telephone and fax)... this can quickly get out of hand!
One issue here is whether all contact types share a superclass; if so,
what would the identifier be? There is a similar issue with the
proposed LegalPerson superclass: is there a real life identifier shared
by organizations and individuals?
Jamie.
--
Jamie Collins
Bob wrote:
> How exactly do I switch to ANSI mode?
About ANSI SQL query mode (MDB)
http://office.microsoft.com/en-us/assistance/HP030704831033.aspx
Jamie.
--
Graham Mandeno
--
Cheers,
Graham
"Jamie Collins" <jamiec...@xsmail.com> wrote in message
news:1155022058.8...@i42g2000cwa.googlegroups.com...
Bob
This doesn't seem to be working properly for me.
Here's what I've done so far:
In tblContacts:
- left the pk as it was (ie tblContactsID remains an autonumber pk field)
- created a new unique multifield index based on ContactID and ContactTypeID
as per the instructions in the Access help file
In tblIndividuals:
- deleted the original autonumber pk field (IndividualsID)
- converted the existing ContactID (number) field as the new pk
- inserted a new ContactTypeID (number) field
- set the "default value" property to 1 (corresponding to the ContactTypeID
for the "Indiv" ContactType in tblContactTypes)
- set the "required" property to Yes
- created a new unique multifield index based on ContactID and ContactTypeID
as per the instructions in the Access help file
In tblOrganisations
- deleted the original autonumber pk field (OrganisationsID)
- converted the existing ContactID (number) field as the new pk
- set the "default value" property to 2 (corresponding to the ContactTypeID
for the "Orgs" ContactType in tblContactTypes)
- set the "required" property to Yes
- created a new unique multifield index based on ContactID and ContactTypeID
as per the instructions in the Access help file
I then created a 1:1 relationship based on the combined ContactID and
ContactTypeID fields between tblContacts and tblIndividuals.
I did this by selected the two fields in tblContacts and dragging them over
to tblIndividuals. I created a 1:1 relationship between tblContacts
and tblOrganisations in the same way.
I then deleted all existing test data from tblContacts, tblIndividuals and
tblOrganisations - starting with a clean slate.
I then opened my client data-entry form. The main form has all fields from
tblContacts. The subform is unbound, but I have
inserted vba into the AfterUpdate event section of the form to ensure that
the SourceObject of the subform control is changed to the required subform
depending on the
selected ContactType (selected from a combo box).
I can enter the first record of either tblIndividuals or tblOrganisations
without difficulty - once I open the required subform the value of ContactID
is
the same as the autonumber pk in tblContacts, and the value of the
ContactTypeID defaults to the relevant default value.
However, after having entered this first record, if I then close and reopen
the main form, I am prevented from creating any new reords in either table
by a
popup box which states "The record cannot be deleted or changed because the
table "Individuals" includes related records."
What could be causing this error? There are no "related" records in
existence!
TIA
Bob
"Graham Mandeno" <Graham....@nomail.please> wrote in message
news:%23Rc1wLn...@TK2MSFTNGP06.phx.gbl...
Graham Mandeno
Your changes to the design sound fine.
The only thing I would add is a validation rule for ContactTypeID:
=1 in tblIndividuals
=2 in tblOrganisations
to ensure that one entity cannot accidentally "morph" into the other.
As to your strange error, are you certain that you are not trying to change
tblContacts.ContactTypeID for an *existing* record (the one you have
previously entered)?
Do you get the error if you are on a new, empty record?
How have you set up the Link Master/Child Fields properties of your subform
control? If you change the SourceObject of a subform control then you must
also respecify the link fields, even though the field names have not
changed.
Also, you should be checking in Form_Current that the appropriate subform is
loaded and changing it if necessary.
If you're still having trouble, post the code behind your form and I'll try
to reproduce the problem.
--
Good Luck!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <fake...@yahoo.com> wrote in message
news:44d8b344$0$21274$5a62...@per-qv1-newsreader-01.iinet.net.au...
Bob
Thanks for sticking with me on this.
My setup is this:
In the unbound subform control I have already the following settings:
Link Child Fields - ContactID;ContactTypeID
Link Master Fields - ContactID;ContactTypeID
I do not create or amend this links programmatically in any way. The only
thing I change via VBA is the SourceObject.
As for the VBA Code itself, this is what I have:
Private Sub cboContactType_AfterUpdate()
If Me.cboContactType.Value = 1 Then ' Individual
Me.Contactsubfrm.SourceObject = "NewIndiv" End If
If Me.cboContactType.Value = 2 Then ' Organisation
Me.Contactsubfrm.SourceObject = "NewOrgs"
End If
End Sub
I've placed this code in the "After Update" event for a combobox in my main
form. The control itself is bound to the ContactTypeID field in my
tblContacts, but the RowSource is bound to my tblContactType.
"NewIndiv" is my modified subform for Individuals, and "NewOrgs" is my
modified subform for Organisations. "Contactsubfrm" is the name I have
given the subform control on my main form.
I've tried adding the following lines in each of the If ... Then statemens
in my code:
Me.Contactsubfrm.LinkChildFields = "ContactID;ContactTypeID"
Me.Contactsubfrm.LinkMasterFields = "ContactID;ContactTypeID"
But this just causes the error message to popup sooner - as soon as the
subform opens rather than when I try to select a control or move to a new
record. This time I get "Run Time 3200" as part of the error message as
well. Curiously, the record selectors on the subform are not grayed out in
this scenario - but still result in an error message if I press any button
on the record selector itself.
As for the validation rules - I forgot to mention that I had already put
these in place (as per the directions in your previous post).
As for the problem itself, it occurs on both subforms:
- when the NewIndiv opens up, the first record it shows is the existing
record that I just entered. The message I quoted earlier pops up regardless
of whether I'm trying to select a textbox on the subform or simply using the
record selector (on either the main form or the subform itself) to create a
new record. (By the way, the record selector on the subform remains grayed
out)
- the message also pops up when I open the NewOrgs subform (which shows a
blank record except for the ContactID and ContactTypeID fields which are
already filled in when the form opens).
I'm not sure what you mean when you say I should be checking in Form_Current
to make sure the appropriate subform is loaded. I can definitely see the
subforms changing depending on the value in my combobox (for ContactType)
if that's what you mean.
TIA
Bob
"Graham Mandeno" <Graham....@nomail.please> wrote in message
news:uYNzw9yu...@TK2MSFTNGP02.phx.gbl...
Graham Mandeno
Is your database very large? Would you mind zipping it and emailing it to
me? That would be quicker than me trying to set up something from scratch
to try to reproduce the problem.
Send it to ng1.g.mandeno at xoxy.net.
--
Thanks!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <fake...@yahoo.com> wrote in message
news:44d90b3c$0$21303$5a62...@per-qv1-newsreader-01.iinet.net.au...
Bob
I just got home from work.
I've emailed you a copy of the database as requested. The file is just of
600KB.
TIA
Bob
"Graham Mandeno" <Graham....@nomail.please> wrote in message
news:OXzB3kzu...@TK2MSFTNGP06.phx.gbl...
Graham Mandeno
Strange... haven't seen it yet.
You might like to try graham at mvps dot org.
--
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <fake...@yahoo.com> wrote in message
news:44d9bfbc$0$25743$5a62...@per-qv1-newsreader-01.iinet.net.au...
Bob
I must've missed your post last night. I've emailed another copy of
the file to your new email address.
Cheers
Graham Mandeno
I found the second one in the spam bucket - it didn't like you for some
reason :-)
Don't know what happened to the first - maybe met the same fate.
Anyway, the problem was that you were not switching the subform in
Form_Current, so it *looked* like you were on a new record but you were
actually changing the ContactType for an existing record.
Try these modifications to your code - most you can just copy and paste:
' since you need to do it in more places than one,
' add a private proc to switch the subform
Private Sub SetContactType()
With Me.Contactsubfrm
Select Case Me.cboContactType.Value
Case 1 ' Individual
.SourceObject = "NewIndiv"
.Visible = True
Case 2 ' Organisation
.SourceObject = "NewOrgs"
.Visible = True
Case Else
.Visible = False
End Select
End With
End Sub
' Call it in both cboContactType_AfterUpdate AND Form_Current
Private Sub cboContactType_AfterUpdate()
Call SetContactType
End Sub
Private Sub Form_Current()
Call SetContactType
End Sub
' now, the icing on the cake to get rid of those nasty unfriendly messages
Private Sub cboContactType_BeforeUpdate(Cancel As Integer)
Dim sTable As String
Dim sMsg As String
If Not IsNull(cboContactType.OldValue) Then
Select Case cboContactType.OldValue
Case 1
sTable = "Individuals"
Case 2
sTable = "Organisations"
End Select
If DCount("*", sTable, "ContactID=" & Me.ContactID) <> 0 Then
sMsg = "If you change the type of this contact, then you must " _
& "first delete all related information from the " & sTable _
& " table." & vbCrLf & vbCrLf & "Do you really want to do this?"
If MsgBox(sMsg, vbQuestion Or vbYesNo Or vbDefaultButton2) _
= vbYes Then
CurrentDb.Execute "Delete * from " & sTable _
& " where ContactID=" & Me.ContactID, dbFailOnError
Else
Cancel = True
cboContactType.Undo
End If
End If
End If
End Sub
You should change your VBA project references too (Tools>References).
Remove the reference to ADO (Microsoft ActiveX Data Objects 2.x) and add one
to DAO (Microsoft DAO 3.6).
Also, I suggest you make Contacts.ContactTypeID a required field.
Finally, make your subforms both Single form view (not continuous or
datasheet) and remove all record selectors and navigation buttons.
Let me know how you get on :-)
--
Good Luck!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <boblan...@yahoo.com> wrote in message
news:1155179612.1...@i3g2000cwc.googlegroups.com...
Bob
Thanks alot Graham. It's finally working. :-)
Just one more question though, why do you prefer DAO over ADO? I've now
acquired a copy of the "Microsoft Office Access 2003 Bible" and there's a
small section in it that asserts that ADO is to be preferred over DAO
because Microsoft does not plan to provide any future enhancements for the
latter. I'm still starting out at this, so I'm not entirely clear on the
other pros and cons of each.
Regards
Bob
"Graham Mandeno" <Graham....@nomail.please> wrote in message
news:%23wgMY5G...@TK2MSFTNGP04.phx.gbl...
Bob
Actually I did have another question too - more out of curiosity than
anything else.
You mentioned earlier that to switch to ANSI-92 mode you need to go to Tools
> Options > Tables/Queries. When I following these directions I get a form
with a Table and a Query design section. In the Table design section, I get
options to change the default field sizes, the default field type, and a box
for "AutoIndex on Import/Create". In the Query design section, I get
checkboxes to "show table names", "output all fields" and "enable autojoin".
I also get radio buttons to "Run permissions" as "Owner's" or "User's".
But I don't see anything that refers to ANSI mode. Any ideas why?
Regards
Bob
"Bob" <fake...@yahoo.com> wrote in message
news:44db4b95$0$15957$5a62...@per-qv1-newsreader-01.iinet.net.au...
Graham Mandeno
Glad it's all working :-)
One thing I forgot to say was you should change your PK field
"ContactTypeID" from AutoNumber to Long integer. When you have values
hard-coded in your app, it makes no sense to have Access automatically
generating those values for you!
On the DAO/ADO thing, I could not disagree more with the authors of "The
Bible" (was that blasphemy? <g>)
DAO is the native object model for Jet databases and, as such, is the
"natural" way of communicating with them. ADO is a sort of Esperanto, and
while it can achieve most things, albeit in a sometimes inefficient way,
there are some things which require DAO.
There were rumours flying around about 4-5 years ago that "DAO is dead", and
that there would be no further development to the Jet engine, but this has
proved very wrong, as can be seen from what has happened with Access 2007.
At about that time, Mary Chipman, who most would consider a High Priestess
in this area, wrote the following article:
http://sqlserveradvisor.com/doc/05515
She also made this statement in a private forum, which I'm sure she would
not mind being quoted:
<quote>
DAO was designed, customized, and tweaked specifically for the Jet
engine. In an all-Access application, it will give you the best
performance and the most complete feature set. It will undoubtedly
continue to be supported as long as Jet ships as a database engine for
Access. If you only program in Access against Jet, you probably won't
ever need ADO.
ADO was designed as a general-purpose data access wrapper around OLE
DB and is not specific to a particular engine. If your Access
application makes use of SQL Server data, then ADO will be a better
choice when writing data access code (and is in fact used in an ADP
where the Jet engine isn't present). DAO uses the Jet engine, which
adds unnecessary overhead when coding against SQL Server, etc. If for
some reason you can't use ADO, then ODBCDirect is a better choice when
coding against SQLS because it bypasses Jet.
You don't need to worry about learning ADO.NET unless you're building
a VS.NET windows forms or an ASP.NET app, because it doesn't work in
Access or any other COM apps--it requires the .NET Framework. The
other developers you spoke to are right--ADO.NET is really a new and
different technology that bears only a superficial resemblance to
classic DAO/ADO. However, you still may need to learn ADO if you land
a project that isn't being built using .NET -- VB6 will undoubtedly be
around for years to come.
Yes, the alphabet soup of data access technologies is confusing -- but
there's sound technical reasons why you'd choose one data access
method over another in a given situation.
<\quote>
--
Good Luck!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <fake...@yahoo.com> wrote in message
news:44db4b95$0$15957$5a62...@per-qv1-newsreader-01.iinet.net.au...
Graham Mandeno
(This would also explain why your VBA references were set to ADO by default,
and not DAO)
You don't want SQL-92 anyway, if you are working with a Jet database.
--
Cheers,
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <fake...@yahoo.com> wrote in message
news:44db5289$0$15974$5a62...@per-qv1-newsreader-01.iinet.net.au...
Bob
Yes, I run Access 2000 at home. We have access 2003 at work and I just
found the right settings on that one. I'll keep away from it anyway,
but its nice to know where the option is if I ever need it.
By the way, I think I found a slight bug in the Before_Update code you
supplied. What I have found is if I try to change the ContactType the
custom error message popups up as expected. If I then opt to delete
the existing record, everything is fine. The record is deleted and I
can still navigate the records using the record selector at the foot of
the main (Clients) form - again everything works as expected. But if I
opt to cancel the update instead, I end up getting the standard Access
message about not being able to change or delete the record (ie the one
I was getting before you came to the rescue :-) ).
I came to the conclusion that the "cboContactType.Undo" line simply
wasn't working. After looking in the help files on the "dirty" event,
I noticed this statement:
"The BeforeUpdate and AfterUpdate events for a record occur after you
have entered the new or changed data in the record and moved to another
record (or clicked Save Record on the Records menu), and therefore
AFTER the Dirty event for the record." (my emphasis)
So I focussed on the dirty event. Anyways, for the benefit of those
who might have been following this thread, I resolved the problem by
simply adding "Me.Form.Undo" in the line immediately after the existing
undo command.
These variations also worked ("Clients" is the name of my main form):
(1) Forms!Clients.Undo
(2)
If Forms("Clients").Dirty = True Then
Forms("Clients").Undo
End If
Everything seems to be fine now. Thanks again for all your help on
this issue.
Getting back to the ADO/DAO, my long term aim would be ultimately to
port my little Access program to VB.Net - purely because I'm a sucker
for punishment :-)
If I code everything using DAO now, will I need to re-code everything
into ADO later, or does VB.Net not care which one you reference?
On a different tangent, if I port everything over to VB.Net, do you
know if I will need extra licences or if I have to upgrade to a
developer edition of some sort before I can distribute my VB.Net
program with an .mdb file? Will my VB.Net or existing ms office
licences cover this sort of thing (ie distribution)? And what's the
deal with runtime files? Will they be packaged with my .mdb file if I
incorporate that into a VB.Net program?
Thanks for letting me pick your brain.
TIA
Bob
Graham Mandeno
Answers inline...
> By the way, I think I found a slight bug in the Before_Update code you
> supplied. What I have found is if I try to change the ContactType the
> custom error message popups up as expected. If I then opt to delete
> the existing record, everything is fine. The record is deleted and I
> can still navigate the records using the record selector at the foot of
> the main (Clients) form - again everything works as expected. But if I
> opt to cancel the update instead, I end up getting the standard Access
> message about not being able to change or delete the record (ie the one
> I was getting before you came to the rescue :-) ).
That's annoying, isn't it? I reckon that this is a bug in Access. It
recognises that you have changed one of the fields in the relation but fails
to recognise that you have undone that change.
I have discovered a workaround, and that is to set the cascading updates
property on the relations between Contacts/Individuals and
Contacts/Organisations. That way, Access doesn't whinge when you change the
master side of the relationship - it just updates the foreign key field to
the same value as it had before. Of course, you can't really change the
value of Contacts.ContactTypeID because the constraint in the related table
allows only one valid value.
So... make this change and remove the extra Undo.
By the way, the correct form to use if you want to undo the entire form is:
Me.Undo
Me is already a form object, so Me is equivalent to Me.Form.
The reason you don't want to undo the entire form is that you might have
changed a whole lot of other fields in your Contacts record before
inadvertently changing the contact type. You are then stuck between the
rock and the hard place - either delete the related record and lose all the
indiv/org data, or undo the current record and lose all your changes.
> Getting back to the ADO/DAO, my long term aim would be ultimately to
> port my little Access program to VB.Net - purely because I'm a sucker
> for punishment :-)
You certainly are :-)
this will be a complete rewrite. there is no easy way to convert an Access
app to .Net (or VB6 for that matter).
> If I code everything using DAO now, will I need to re-code everything
> into ADO later, or does VB.Net not care which one you reference?
I believe you can use the DAO object model from .Net - no reason why not.
> On a different tangent, if I port everything over to VB.Net, do you
> know if I will need extra licences or if I have to upgrade to a
> developer edition of some sort before I can distribute my VB.Net
> program with an .mdb file? Will my VB.Net or existing ms office
> licences cover this sort of thing (ie distribution)? And what's the
> deal with runtime files? Will they be packaged with my .mdb file if I
> incorporate that into a VB.Net program?
No, you don't need any licences to open an MDB using .Net or VB6. All you
need is DAO360.DLL, but I'm pretty sure this comes with Windows anyway.
If you buy Visual Studio Tools for Office (VSTO) you get with it the Access
Developer Extensions (ADE) which allows you unlimited licence to distribute
the runtime version of Access, so you can install and run your Access app on
a computer that doesn't have Access (or even Office) installed.
> Thanks for letting me pick your brain.
My pleasure :-)
--
Good Luck!
Bob
I was a bit worried about Form.Undo myself (for the very reason you warn
against using it) - but it seems that access auto-saves any changes
everytime you move (eg tab) to the next field anyway. So I figured I was
safe or at worst would lose changes only to the current field. Your
solution is, of course, much better. I updated the relationships and
removed the extra undo and everything works. Thanks yet again.
As for porting to VB.Net, the learning curve for Access just seems a little
easier to climb than VB.Net; especially when you have very little spare
time. While I always enjoy pulling my hair out (to the point that I'm sure
I'm experiencing premature balding :-D ), I'm also keen to see some
progress. With Access, I hope to see a working prototype a little sooner.
I was rather hoping that the required runtime files might come with VB.Net
itself. I guess I'll have to invest in a copy of VSTO.
While I still have your attention, I'd like to ask a new question related to
form/subform design. I would like to move all of my contact phone and fax
numbers into a new table (tblTeleComs). I have created a Junction table
tblContactComs to enable a many to many relationship between tblContacts and
tblTeleComs. The table structions for the two new tables are as follows:
tblTeleComs
ComID (pk - autonumber)
ComType [to store text descriptions like "Work Tel" or "Home Tel")
ComNumber
tblContactComs
ContactID (pk - number)
ComID (pk - number)
I've created a new subform (subfrmContactNumbers) which I have set up as a
continuous form. This subform is linked to tblTeleComs.
What I would like to do is have two subforms on my existing main form. I
want my existing subform (NewIndiv/NewOrg) to go on the left, and my new
form to sit immediately to the side of that. This way all phone and fax
numbers will run down the right hand side of the main form. I want to the
user to be able to add new numbers on this form by simply pressing a command
button - and have a new blank row appear immediately below the existing fax
and phone numbers ready for a new number to be inserted. (I hope this is
clear).
Anyway, my problem is that I don't have a ContactID in tblTeleComs so how do
I link the new subform to my main form?
TIA
Bob
"Graham Mandeno" <Graham....@nomail.please> wrote in message
news:emCzGZcv...@TK2MSFTNGP03.phx.gbl...
Bob
Don't trouble yourself with my last query. I got access to create a new
form using my junction and TeleComs table and then used the resulting form
as my source for the subform control in my main form. This achieves what I
want except that the control does not automatically resize to enable all
records in the subform to be seen. Is there a way to do this?
Regards
Bob
"Bob" <fake...@yahoo.com> wrote in message
news:44dd93cf$0$15994$5a62...@per-qv1-newsreader-01.iinet.net.au...
Graham Mandeno
No doubt you worked out that you should base your subform's recordsource,
not on tblTeleComs, but on a query comprising both tblTeleComs AND
tblContactComs. That way you have a ContactID in your recordsource to be
the link child field.
The total height required by a form may be calculated as follows:
(<height of detail section> * <number of records>) + <height of header and
footer (if present)>
In VBS terms:
Public Function FormHeightRequired(frm as Form) as Long
Dim lHeight as Long
With frm
.RecordsetClone.MoveLast
lHeight = .Section(acDetail).Height * .RecordsetClone.RecordCount
On Error Resume Next
' in case no header/footer
lHeight = lHeight + .Section(acHeader).Height +
.Section(acFooter).Height
FormHeightRequired = lHeight
End With
End Function
You can call this in the Current event proc of your main form to set the
height of the subform.
With Me.[SubformControl]
.Height = FormHeightRequired(.Form) + <some constant>
End With
The <some constant> is an extra bit you will have to fiddle with to
accommodate the subform control's border. Start with about 30.
You probably want to specify a limit, in case the required space is not
available. In this case, you can turn on a vertical scrollbar for the
subform:
.Form.ScrollBars = 2 ' vertical only
or, if there is enough space:
.Form.ScrollBars = 0 ' no scrollbars
--
Good Luck!
Graham Mandeno [Access MVP]
Auckland, New Zealand
"Bob" <fake...@yahoo.com> wrote in message
news:44ddaaa1$0$15953$5a62...@per-qv1-newsreader-01.iinet.net.au...
Graham Mandeno
just arrived this morning.
God knows where it's been! :-)
--
Cheers,
Graham
Bob
Regards
Bob
"Graham Mandeno" <Graham....@nomail.please> wrote in message
news:u26xRr0v...@TK2MSFTNGP05.phx.gbl...