There is no standard answer to this question. Consider matching fields
that should be different between records and could denote
the record as unique. For example, in a standard contact database, the name, address, and phone number
should identify a unique person. Many people can have the same city and
state, so these would be less meaningful.
It is important to understand the relationship between using multiple
fields and how much importance, or weight, is to be given to each
field being considered in the matching process. For example, Name might not be as important
as Address and ZIP, so weighting Name less than Address and ZIP
can result in more matches where the Address and ZIP are exact, but the Name
has scored less than an exact match.