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

Late to the party but I wanted to add my two cents:

Should each and every table have a primary key?

• If you are talking about "Relational Albegra", the answer is Yes. Modelling data this way requires the entities and tables to have a primary key. The problem with relational algebra (apart from the fact there are like 20 different, mismatching flavors of it), is that it only exists in paper. You can't build real world applications using relational algebra.

• Now, if you are talking about databases from real world apps, they partially/mostly adhere to the relational algebra, by taking the best of it and discarding the rest. Also, database engines offer massive non-relational functionality nowadays (it's 2020 now). So in this case the answer is No. In any case, 99.9% of my real world tables have a primary key, but there are justifiable exceptions. Case in point: event/log tables (multiple indexes, but not a single key in sight).

Bottom line, in transactional applications that follow the entity/relationship model it makes a lot of sense to have primary keys for almost (if not) all of the tables. If you ever decide to skip the primary key of a table, make sure you have a good reason for it, and you are prepared to defend your decision.