Primary Property

Applies To Index.

Description

You can use the Primary property to specify the primary key field for a table. A primary key field holds data that uniquely identifies each record in a table.

Setting

The Primary property uses the following settings.

Setting	Description	Visual Basic

Yes	The selected index is the primary key.	True (–1)
No	The selected index isn't the primary key.	False (0)

You can set the Primary property in three ways:

In table Design view, select the field or fields in the order you want for the primary key and then click the Primary Key button on the toolbar.
In the Indexes window, select or enter the name of an index in the Index Name column and set the Primary property to Yes in the Index Properties section.
In Visual Basic, to access the Primary property of an index, use the DAO Primary property.

Remarks

Microsoft Access automatically creates an index on the primary key field of a table and uses it to find records and to create joins between tables. The primary key index requires an entry in each primary key field and allows no duplicates. The order of the fields in a multiple-field primary key determines the default sort order for the table.

If there is no primary key when you save a table's design, Microsoft Access will display a dialog box asking whether you want a primary key to be created. If you click Yes, an AutoNumber data type field will be added to the table (with its NewValues property set to Increment) and set as the primary key. If you click No, no primary key will be created.

A table with no primary key can't be used in a relationship and can be slower to sort and search.

See Also Index object ("DAO Language Reference"), Indexed property, Primary property ("DAO Language Reference"), Unique property, Unique property ("DAO Language Reference").