Can a database table be without a primary key?

Question

Can anyone tell me if a table in a relational database (such as MySQL / SQL SERVER) can be without a primary key?

For example, I could have table day_temperature

Answer 1

If the possibility of having duplicate entries (for example for the same time) is not a problem, and you don't expect to have to query for specific records or range of records, you can do without any kind of key.