how to create relationship between tables whwn unvoidable redundancy is there?

[brajbio.22]

If there is lot of redundancy in data in two columns in the table, and other child tables,and it can't be avoided , how we can establish relationship, between parent and child table i.e is there any possibility for establishing realation using primary,unique and foreign key. is composite key a solution for this?

[guelphdad]

compound key is most likely the way to go. can you show some sample data so we can get an idea if that is the best solution for you?