Differences Between Temporary and Permanent Relationships (133357)
The information in this article applies to:
- Microsoft Visual FoxPro for Windows 3.0
This article was previously published under Q133357 SUMMARY
Relationships between tables can be established to link the tables together
based on matching values in a field common to all the tables. The
relationships can be created to exist from one FoxPro session to another
(permanent or persistent) or temporarily for each time a table is used.
Each type relationship is created differently and exists or behaves, in
Visual FoxPro, differently.
Generally, both types of relationships are used regularly in Visual FoxPro
programming.
MORE INFORMATIONPermanent or Persistent Relationships
Permanent or persistent relationships can only exist between tables stored
in a database container (as opposed to free tables). The relationship
itself is stored within the database container and therefore can exist from
one Visual FoxPro session to another until the relationship is explicitly
terminated.
Persistent relationship can be created in the Database Designer using the
table indexes (as opposed to using the table fields).
Because persistent relationships are stored in the database container
certain functions can use these relationships as default links. Each time
the tables involved in the persistent relationship are used in the Query,
View, or Data Environment Designers, these persistent relationships are
used as the default links. Persistent relationships are used to store
referential-integrity information.
Temporary Relationships
Temporary relationships can exist between free tables or tables stored in a
database container. However, temporary relationships cannot be created
between a free table and a table in database container.
To create temporary relationships, use the SET RELATION TO command or
create them visually in the View window. They must be recreated each time
the table is used.
Another major difference between a Persistent and Temporary relationship is
that the Temporary relationship causes the record pointer in the child
table to move automatically when the parent record pointer moves.
REFERENCES
Additional information regarding the definition, creation and removal of
Persistent and Temporary relationships can be found in the Visual FoxPro
Help menu and in the Visual FoxPro User's and Developer's Guides: Visual
FoxPro User's Guide, Page 67; Developer's Guide, Pages 131, 183.
| Modification Type: | Major | Last Reviewed: | 2/15/2000 |
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| Keywords: | KB133357 |
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