Should all database tables have a primary key?

Question

Is it good practice to give every database table a primary key? It seems to me that if the primary key is not explicitly needed, then it would just be extra clutter in my d

Answer 1

When you probably WOULD:

In an OLTP database you'd almost always (in my case always) have a primary key of some sort. Sometimes Guid, sometimes autonumber/identity fields, sometimes set by the application or the customer. Sometimes even a combination of more than one field. This is because you'll typically want to uniquely identify any given row from the table.

Also, a primary key is a constraint used by the query optimiser that should improve performance for lookups and joins.

When you probably WOULDN'T:

The only time you wouldn't have a primary key is in a "reporting" table, probably in a denormalised data warehouse.