begginer question

Hi everyone I just need something that I believe is very simple only I can't find an answer for it anywhere I have a database that each row has a machine, its serial, the customer and other details. The problem is that I have customers with more than one machine and I need to query for all the rows, but I don't want the rows that contain duplicate customers. The problem is that the only way for me to know the right row from let's say 3 rows that contain the same customer name is the serial number which needs to be the higher. So all I need a query to do that. Thanks in advanced Ziv