The Purpose of the Primary Key in Access

Microsoft Access uses primary keys to uniquely identify each record in a table. The database administrator defines a primary key when he creates tables. He selects a field or fields and clicks the "Primary Key" button on the Design tab.

Function

In Access, each table can have only one primary key created from one or more fields. A primary key made from multiple fields is a composite key. In this case, two records can contain the same data in some primary key fields, but the data in all primary key fields must be unique to each record.

Features

When creating multiple tables in a database, an administrator can link two or more tables together. He can link a primary key from one table to another table, using it as a foreign key. The foreign key can then act as a primary key in the second table on its own or in conjunction with another field.

Considerations

An administrator can create a primary key with an auto-increment feature. When entering records into the database, the primary key acts as an index that guarantees no duplicates in the primary key field. This ensures the uniqueness of each record, even if every other field has duplicate information.

References

• Microsoft Office: Create or remove a primary key
• Blue Moose Technology: Selecting the Right Primary Key in Microsoft Access