PRB: Uniqueness of Index Violated When Creating Primary Index

• Microsoft Visual FoxPro for Windows, versions 3.0 and 3.0b

SYMPTOMS

After you create a Primary Index for a table that is populated with records and choose to make the structure changes permanent, the following error message appears:

   Uniqueness of index <name> is violated.

CAUSE

More than one record, including any deleted records, contain the same value within the field being used for the Primary Index. This also applies to the existence of more than one blank record, whether marked for deletion or not.

RESOLUTION

Eliminate any use of the same value within multiple records. There are many methods you could use, but perhaps the easiest is to use a query. The following example query will generate a cursor that contains a list of the values that occur in more than one record of a table:

   SELECT <field name> FROM <table name>;
      GROUP BY <field name>;
      HAVING COUNT(<field name>) > 1

   ARTICLE-ID: Q115617
   TITLE     : How to List Duplicate Records in a Field

   ARTICLE-ID: Q104332
   TITLE     : Methods of Deleting Duplicate Records from a Database

   !DELETED()

   ARTICLE-ID: Q139756
   TITLE     : Cannot Reuse Deleted Primary Key Values in Visual FoxPro

STATUS

This behavior is by design.

MORE INFORMATION

The intent of a primary index is to never permit duplicate values on the specified fields. For more information about primary indexes, search for "primary index" in the Visual FoxPro Help file.

Steps to Reproduce Behavior

1. Create a new table that has two fields. In this case, the table is called States and the fields are Fullname (Character, 15) and Abbrev (Character, 2).

2. Add the following records to the table:

      Fullname     Abbrev
      -------------------
      Alabama      AL
      Alaska       AK
      Arizona      AZ
      Arkansas     AR
   
   

3. Add two blank records to the table, and mark them for deletion, but do not pack the table.

4. On the Window menu, click View Window, and if the States table isn't open, click Open. Then select it.

5. Click the Properties button, and from the Work Area Properties window, click the Modify button.

6. Click the Index tab in the Table Designer, and enter state for the Name, set Primary as the Type, and Fullname for the Expression.

7. Click OK. Within the message box asking to make structure changes permanent, click Yes. At this point, the following error appears:

   Uniqueness of index state is violated.