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

<p>I read a lot of articles/discussions/newsgroups posts saying that it's better to use unique constraint (aka unique index for some db) instead of PK.</p>

<p>What's your point of view?</p>

Can you provide references to these articles?
I see no reason to change the tried and true methods.  After all, Primary Keys are a fundamental design feature of relational databases.
Using UNIQUE to serve the same purpose sounds really hackish to me.  What is their rationale?
Edit: My attention just got drawn back to this old answer.  Perhaps the discussion that you read regarding PK vs. UNIQUE dealt with people making something a PK for the sole purpose of enforcing uniqueness on it.  The answer to this is, If it IS a key, then make it key, otherwise make it UNIQUE.