Should each and every table have a primary key?

Question

I\'m creating a database table and I don\'t have a logical primary key assigned to it. So, I\'m thinking about leaving it without a primary key, but I\'m feeling a bit guilt

Answer 1

Disagree with the suggested answer. The short answer is: NO.

The purpose of the primary key is to uniquely identify a row on the table in order to form a relationship with another table. Traditionally, an auto-incremented integer value is used for this purpose, but there are variations to this.

There are cases though, for example logging time-series data, where the existence of a such key is simply not needed and just takes up memory. Making a row unique is simply ...not required!

A small example: Table A: LogData

Columns:  DateAndTime, UserId, AttribA, AttribB, AttribC etc...

No Primary Key needed.

Table B: User

Columns: Id, FirstName, LastName etc. 

Primary Key (Id) needed in order to be used as a "foreign key" to LogData table.