Primary Key versus Unique Constraint?

Question

I\'m currently designing a brand new database. In school, we always learned to put a primary key in each table.

I read a lot of articles/discussions/newsgroups posts

Answer 1

posts saying that it's better to use unique constraint (aka unique index for some db) instead of PK

i guess that the only point here is the same old discussion "natural vs surrogate keys", because unique indexes and pk´s are the same thing.

translating:

posts saying that it's better to use natural key instead of surrogate key