Using one-to-one relationship

Anonymous
2011-02-07T01:32:55+00:00

For various reasons, I need to break up a large table into smaller tables.  I've set up the smaller tables with one-to-one relationships.

If I assign a form's record source using just one of the smaller tables (and its fields), the form opens correctly showing the first record.  And, I can move through all the records using the Access record controls.

If I add one or more of the smaller tables (which participate in the one-to-one relationship with the original table), the form opens but no records are available - i.e., it opens as if I asked it to display a new record, and it doesn't recognize that there are other records available.

The one-to-one relationships are correctly set, with each table's primary key being a single key.

I have form controls that need to be bound to several of the one-to-one tables, so several tables need to be the form's record source.

As an example:  Table A has an autonumber primary key field, AID, and another field, Aname.  Table B has a primary key field BID (numeric long integer type) joined to AID in a one-to-one relationship (with referential integrity), and another field, Baddress.

If Table A is a recordsource for a form, the value of field Aname appears on the form and I can move through all Table A records.  As soon as I add Table B (along with Table A) as a recordsource, the form opens with no records available (i.e., a blank form as if I told it to go to a new reocrd).

I realize I can resolve this through a single large table, but that's what I'm trying to avoid. 

Has anyone worked with one-to-one relationships enough to have run into this problem?  And come up with a solution?

Thanks for any help.

Mike

Microsoft 365 and Office | Access | For home | Windows

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ScottGem 68,840 Reputation points Volunteer Moderator
2011-02-10T19:13:03+00:00

Mike,

I'm going to agree with Roger yet again. Helping you has been a pleasure and we will be here to support you as your project continues.

The main difference between bound and unbound forms is that, with a bound form, Access handles all the I/O between the form and the table. With an unbound form, the user has to write code (VBA), to handle the I/O. The complexity of that code can vary widely depending on the usage and purpose of a form. For example, a form solely for entering new records is fairly easy to code. But a form for retrieving data and populating the unbound controls, can be very complex. The coding involved depends on the table structure and form layout. Personally, I'm lazy and tend to use bound forms wherever I can.

There is only ONE circumstance in Access where a child record can be created with an automatically populated FK. And that's when using a subform. When you correctly link a subform to the main (parent) form, then any records created in the subform have the FK automatically populated. This is one of the reasons I said that subforms are a very powerful feature. But this only works with bound forms. So, in every other circumstance, when you add a record to a child table, you have to make sure the FK is populated correctly.

Hope this helps, Scott<> P.S. Please post a response to let us know whether our answer helped or not. Microsoft Access MVP 2010 Blog: http://scottgem.wordpress.com Author: Microsoft Office Access 2007 VBA Technical Editor for: Special Edition Using Microsoft Access 2007 and Access 2007 Forms, Reports and Queries

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Anonymous
2011-02-10T18:15:24+00:00

Mike,

It's posts like this that makes the whole process of answering questions here worth while.  I think we've seen a lightbulb go off above your head <grin>

As you no doubt realize, there are two distinct knowledge sets necessary for database development: design and implementation.  The Design set is universal and can be applied to any DBMS implementation.  The Implementation set is specific to the DBMS.

For Design knowledge, I recommend Michael Hernandez' "Database Design for Mere Mortals".  I taught 12 years of college courses in db design from that book.  It was a revelation to me.

For Access Implementation knowledge, I recommend "Access Cookbook" by Ken Getz, Paul Litwin, and Andy Baron.  I learn best from examples and this book is a set of common problems and solutions in Access development.  It's not really a book that you read through.  It's best used to find how to solve a specific problem.

I created the samples on my website (www.rogersaccesslibrary.com) with the same idea in mind. 

Good luck!

-- Roger Carlson

MS Access MVP 2006-2010

www.rogersaccesslibrary.com

If you want a detailed answer, ask a detailed question!

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  1. Anonymous
    2011-02-09T18:36:07+00:00

    Scott:

    I forgot to mention - "frontend", "backend" is just my terminology to distinguish between a project's evaluation phase, and the later management/stewardship phase.  It has nothing to do with how a db is distributed on a network.  Sorry about the confusion.

    Mike

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  2. Anonymous
    2011-02-09T18:26:30+00:00

    Scott/Roger:

    I'm beginning to see the light.  Roger - I reviewed the pages on the link you provided - thanks.

    As I mentioned earlier, I am pretty ignorant on subforms, although I've reviewed Access documentation about them (which seems kind of skimpy to me, at least in answering the questions I have).  BTW, I'm a retired engineer and an old, out of practice, application programmer.  I've tried to pick up Access recently to help out a local non-profit (the land trust - they work on conserving local land tracts for environmental purposes).

    I think I'm starting the understand the power of the data model you're suggesting.  Now, if y'all will let me impose on you further, I'd like to understand the implementation details.

    For simplicity, let's assume Scott's two table setup.  And, for tluMilestones/Milestone, let's assume values like:  project initiation date, site visit date, evaluation complete (Y/N logical), board vote date.

    I'd start the user data entry with a Project Coordination Form (PCF).  To start a new project, the PCF would open and the user would enter initial data like Project Name, and Property and Owner info (these last two are entered via a separate form/table (1:many) linked via ProjectID.  Then, the user would open a Phase One Evaluation Form (POEF).

    The POEF gathers site evaluation and site visit information.  Amongst other controls, I'd have a project initiation date control and a site visit date control.  And, here is where my subform confusion starts.

    To the extent I understand, you seem to suggest that (for instance) the project initiation date control be a list/combo box with a recordsource set to tluMilestones, from which the user would select "project initiation date", which would then open/move to a subform to enter the project initiation date into tblProjectMilestones linked to the current ProjectID.  Or, a control whose recordsource is preset to MilestoneID/"project initiation date", that opens/moves to the subform.  Or, a  control whose record source is preset to MilestoneID/"project initiation date", and somehow enters the initiation date directly into tblProjectMilestones.

    My confusion is obvious.  There's no sense asking many other questions at this point because they depend on understanding this step.  But, it is not clear to me the different "flavors" that subforms come in.  For instance, I'd like to use an actual custom form (not a datasheet) that opens in a separate window (or, at least, on separate pages of a tab control).

    Thanks again for your help and patience.  And, Scott, thanks for your persistence in not giving me the easy answer.

    Mike

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  3. Anonymous
    2011-02-09T14:15:08+00:00

    I can assure you that amongst all the 1-1 tables there is no duplication of information, and where useful, they make use of other 1-many tables (e.g., Owner Information, Property Information). 

    So, I can provide much more detail (like the table fields), but I doubt it would be helpful for you.  The fields simply represent all the extensive process steps necessary to evaluate a potential property for the trust.

    Mike

    Legitmate uses for 1-1 relationships are so rare, that I can guarantee your database is not designed properly.  The fact that you use the plural to describe some of your fields (criteria, memos, evaluation judgments) shows that.  I assume you've got multiple columns for, say, each memo.  Repeated columns are also a sign of a non-normalized database.  On my blog, I've got a post called Why Normalization? which describes what's wrong with repeated columns.

    As Gina said, you're modeling it as if it's a spreadsheet rather than a database.  The problems you are having now are simply the beginning.  By continuing with this model, you will run into more and more problems that a proper design would all but eliminate. 

    -- Roger Carlson

    MS Access MVP 2006-2010

    www.rogersaccesslibrary.com

    If you want a detailed answer, ask a detailed question!

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