The standard select query locates records that meet a criterion, such as orders made by a particular customer during a given month. However, you might also be interested in finding those customers who placed more than one order in a month. If all orders for a month are recorded in the same table, you could create a Find Duplicates query to locate CustomerID values that occur more than once in the table.
Click the Create tab.
Click Query Wizard.
Click Find Duplicates Query Wizard.