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

It's not required, but be sure that you don't ever need one. The purpose of the primary key is so that you can uniquely identify one row from another based on a (usually minimal) set of criteria. This allows the database to ensure that you don't have duplicate data, for example, which also allows your database to conform to 1st normal form. If this isn't required then you don't need a primary key, but think carefully about it first.

Don't forget that the primary key doesn't necessarily have to be an additional column that contains an arbitrary unique value - it can also be a set of columns which together define uniqueness (e.g., a person's first name, last name and date of birth in an address book table).