Create a single-field index

1. Open a table in Design view.
   
   
2. In the upper portion of the window, click the field that you want to create an index for.
   
   
3. In the lower portion of the window on the General tab, click in the Indexed property box, and then click Yes (Duplicates OK) or Yes (No Duplicates).

   Click Yes (No Duplicates) if you want to ensure that no two records have the same data in this field.