A table may have more than one key,each key is  called a candidate key. E.g( 1) A table CUSTOMER consists of columns: Customer_Id,name,Address etc.. Customer_Id is the only key (unique),thus a candidate key. E.g(2) consider a table CAR where we can have 2 keys namely license_no,serial_no (which should be unique). Both license_no and serial_no are candidate … Read more