Create a Primary Index in a Visual FoxPro Program
This article describes how to create a Primary Index in a Visual FoxPro Program.
Original product version: Visual FoxPro
Original KB number: 130601
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.
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
Create a new database, or open an existing one.
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
Open the database used in example 1.
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
Add a new table to an existing database with this command:
CREATE TABLE noprime (cLast C(20))
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
ALTER TABLE noprime ALTER COLUMN cLast C(20) PRIMARY KEY