What normal form does a surrogate key violate


I have following question:

"What normal form does a surrogate key violate?"

My thought was the 3rd normal form, but I'm not quite sure it's just an assumption i am making. Could someone explain that to me?

Best Answer

Arguably a surrogate key is not the natural key of the table, so it could be said to violate the 'nothing but the key' principle of 3NF. In practice a surrogate key is just a place holder for the natural key, so this argument is academic at best.

Some obscure normal forms require composite keys to become relevant. 5NF comes to mind in this case as it requires multiple overlapping composite keys on a M:M relationship for a 5NF violation to be possible.