title: Physical Pkey in Fact table
body: <p>I was in an interview. I did some code for them and they were keen on why there is no PKEY in Fact table, why there is duplicate data.  In my opinion, FACT holds foreign keys from dim and there is no need of  Physical PKEY. And on obvious point foreign key column will have duplicates. That whats its purpose is. To show me different fact across different stages. Now, Logically some composite key can make up as primary in fact table but is it good scenario to have that as physical in database.</p>
  
  <p>Summarizing my question.
  1. Does FACT should have primary key physically?
  2. Can we have physical PKEY on set of fkey column( i dont think ms sql will allow this) ?
  3. Does FACT should have surrogate key just for a sake of a pkey? We can have ordering on other important column like date?</p>
  
  <p>Response is awaited want to understand the different opinion on this.</p>