KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q141083: PRB: No Error Message When Creating a Cyclic Relation

Article: Q141083
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b
Operating System(s): 
Keyword(s): 
Last Modified: 11-DEC-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b 
-------------------------------------------------------------------------------

SYMPTOMS
========

In the Database Container (DBC), a table can be related to itself to create a
cyclic relationship. No error message is displayed when the relation is drawn
between two tags of the same table. On the other hand, the SET RELATION command
returns an error message when a cyclic temporal relation is created.

CAUSE
=====

The cyclic relation is not a correct "SET RELATION" relation, but is used in
permanent relations for referential integrity purposes.

Relational theory allows a table to be related to itself. For example, in an
employee table, a whole division needs to be deleted. If the table is related to
itself, you can use a cascade rule when deleting the whole division by deleting
the division head.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Create a .dbc file with a table that has two tags of the same type.

2. Type "MODIFY DATABASE" (without the quotation marks) in the Command window.

3. Click one of the index tags, and drag the tag to the second index tag in the
  same table. A cyclic relation is created.

Additional query words: VFoxWin

======================================================================
Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b
Version           : WINDOWS:3.0,3.0b

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.