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Q168521: HOWTO: Reapply Default Values to Reuse/Recycle Deleted Record

Article: Q168521
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Operating System(s): 
Keyword(s): kbvfp300 kbvfp500 kbvfp600
Last Modified: 11-DEC-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0 
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SUMMARY
=======

This article demonstrates how you can retrieve default values for a deleted
record being reused or "recycled" in Visual FoxPro 3.x and 5.x.

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

In Visual FoxPro, the DELETE command does not delete a record physically;
rather, it only marks the record for deletion. Using the RECALL command unmarks
the deleted record.

In order to physically delete a record from a table in Visual FoxPro, use the
PACK command. Using PACK requires the table to be opened exclusively.

In a multi-user environment, it may be difficult to obtain exclusive use of the
file for packing. To work around this problem, you can recycle deleted records
by using the technique illustrated below.

This article assumes you have an existing database and certain fields have
default values in the table.

The following code snippet does the following:

1. Looks for a deleted record.

2. Retrieves the default values from the table in the database.

3. Re-uses the first deleted record found.

If no deleted records are found, a new record is appended:

     LOCAL lcDeleted, dExpr, nCount, a_field[1]
     lcDeleted = set("DELETED")
     SET DELETED OFF

     * Looks for deleted record in the table
     LOCATE FOR DELETED()

     IF FOUND()
        * bring it back to life and blank its fields
        RECALL
        * blank out the contain of the deleted record
        BLANK

       * Retrieve all default values from the base table.
        FOR nCount = 1 to AFIELDS(a_field)
            dExpr = DBGetProp(CursorGetProp("SourceName")+ ;
                    "." + a_field[nCount, 1], "Field", "DefaultValue")
            * if there is a default value, use it
            IF !Empty(dExpr)
               REPLACE (a_field[nCount, 1]) WITH EVAL(dExpr)
            ENDIF
       ENDFOR
     ELSE
       APPEND BLANK
     ENDIF

     SET DELETED &lcDeleted

In order to retrieve default values from the database, the database needs to be
open at all times. If the database is not open, an error occurs.

NOTE: Unused space in memo files will not be recycled. To recover unused space in
memo files, you must issue a PACK MEMO command (which requires that the table be
opened EXCLUSIVELY).

Additional query words:

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Keywords          : kbvfp300 kbvfp500 kbvfp600 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b kbVFP500 kbVFP600 kbVFP500a
Version           : WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Issue type        : kbhowto

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