When you have Excel locate unique values in a worksheet, you create an Advanced Filter that finds every value that occurs within a single column you identify. For example, if you had a list of all sales on a given day, you could identify which sales representatives made at least one sale. One important limitation of finding unique values, however, is that identification works on only worksheets in which the data is limited to the columns in which you want to find unique values. For example, if you had a two-column worksheet listing the OrderID of an order and the sales representative who took the order, every row would have a unique combination of OrderID (which is different for every order) and sales representative. To find sales representatives who had made a sale on that day, you would need to delete the OrderID column.