DOCUMENT:Q130601  11-FEB-2000  [foxpro]
TITLE   :How to Create a Primary Index in a Visual FoxPro Program
PRODUCT :Microsoft FoxPro
PROD/VER:WINDOWS:3.0
OPER/SYS:
KEYWORDS:kbcode

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

 - Microsoft Visual FoxPro for Windows, version 3.0 
-------------------------------------------------------------------------------

SUMMARY
=======

Microsoft Visual FoxPro has a new index type, Primary. The Primary index,
however, cannot be created in a program by using the INDEX command. This article
shows by example how to add or modify a Primary index in a program.

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

A Primary index is an index that never permits duplicate values on the specified
field or expression. The Primary index may be established in the database
container interface or in a program by using the CREATE TABLE or ALTER TABLE
command.

A table with a Primary index must be part of a database and cannot be a free
table. The first example shows how to create a table with a Primary index. The
second example shows how to alter an existing table to change a Primary key. The
third example adds a Primary index to an existing table.

Example 1 - Create a New Table with a Primary Index
---------------------------------------------------

1. Create a new database, or open an existing one.

2. Issue the following command in the Command window to create a table with a
   Primary index on the cSsn key field:

      CREATE TABLE employee (cSsn C(11) PRIMARY KEY, cLast C(20),;
         cFirst C(20))

Example 2 - Modify an Existing Table to change a Primary Index
--------------------------------------------------------------

1. Open the database used in example 1.

2. Issue the following command from the Command window to move the Primary index
   from the cSsn field to the cLast field:

      ALTER TABLE employee DROP PRIMARY KEY ADD PRIMARY KEY cLast TAG cLast

Example 3 - Modify an Existing Table to add a Primary Index
-----------------------------------------------------------

1. Add a new table to an existing database with this command:

      CREATE TABLE noprime (cLast C(20))

2. From the Command window, add a Primary index to the existing table by using
   one of the following commands:

      ALTER TABLE noprime ADD PRIMARY KEY cLast TAG cLast

   -or-

      ALTER TABLE noprime ALTER COLUMN cLast C(20) PRIMARY KEY

Additional query words: VFoxWin

======================================================================
Keywords          : kbcode 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0

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

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.

Copyright Microsoft Corporation 2000.