Create a Primary Index in a Visual FoxPro Program

2020-09-08

This article describes how to create a Primary Index in a Visual FoxPro Program.

Original product version: Visual FoxPro
Original KB number: 130601

Summary

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 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

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

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