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
    2011-02-13T21:39:50+00:00

    Sorry - I don't know what happened to the formatting on my last post.  It should appear like this:

    Ken:

    I think I typed the error message correctly. In any case, you were quite right that I needed to clear the "Required" property. At that point the statement executed correctly and created the new records as it should.

    Now, I'm down to the final step.

    I put a date control as the only control on the subForm, and I'd like to bind it with the correct ProjectMilestoneDate record. For the sake of this example, the MilestoneTypeID within the correct tblProjectMilestones record is the value 1. I had thought that using the following query as the data source for the control would do the trick, (it seems to work as a standalone query) but I get the Name# error in the control:

    SELECT tblProjectMilestones.ProjectMilestoneDate

    FROM Project INNER JOIN tblProjectMilestones ON Project.ProjectID=tblProjectMilestones.ProjectID

    WHERE (((tblProjectMilestones.MilestoneTypeID)=1) And ((tblProjectMilestones.ProjectID)=Project!ProjectID));

    There's probably a simple way to do this that I'm unaware of. Or, perhaps I need to use a macro or VBA statement tied to an event? This should be the last step I need. If you, Scott or Roger can enlighten me, I'd sure appreciate it.

    Mike

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  2. Anonymous
    2011-02-13T21:35:46+00:00

    Ken: I think I typed the error message correctly. In any case, you were quite right that I needed to clear the "Required" property. At that point the statement executed correctly and created the new records as it should. Now, I'm down to the final step. I put a date control as the only control on the subForm, and I'd like to bind it with the correct ProjectMilestoneDate record. For the sake of this example, the MilestoneTypeID within the correct tblProjectMilestones record is the value 1. I had thought that using the following query as the data source for the control would do the trick, (it seems to work as a standalone query) but I get the Name# error in the control: SELECT tblProjectMilestones.ProjectMilestoneDate FROM Project INNER JOIN tblProjectMilestones ON Project.ProjectID=tblProjectMilestones.ProjectID WHERE (((tblProjectMilestones.MilestoneTypeID)=1) And ((tblProjectMilestones.ProjectID)=Project!ProjectID)); There's probably a simple way to do this that I'm unaware of. Or, perhaps I need to use a macro or VBA statement tied to an event? This should be the last step I need. If you, Scott or Roger can enlighten me, I'd sure appreciate it. Mike

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  3. Anonymous
    2011-02-13T16:59:45+00:00

    I think you may have mistyped the error message as you said earlier that the ProjectMileStoneDate column is in the tblProjectMilestones  table.   That being the case it sounds like the ProjectMileStoneDate column does not allow Nulls, i.e. its Required property is True.  If you want to leave this column empty for the users to enter a date late then amend the tblProjectMilestones table's definition by setting the columns's Required property to False (No) in table design view.

    Ken Sheridan, Stafford, England

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