Combo box on form from master table

While displaying a combo box on form from master table, it is necessary to bound primary key of master table to the control while display is mapped to description of the item. This is achieved using following properties

Data property Row Source : SQL string with necessary data elements,
Data property Bound Column : Number of return element in SQL string
Format Property Column Count : set it to number of columns returned in SQL string
Format Column Width : Set the width for display only column and rest as 0