Does 'Select' always order by primary key?

Question

A basic simple question for all of you DBA.

When I do a select, is it always guaranteed that my result will be ordered by the primary key, or should I specify it wit

Answer 1

It depends on your DB and also it depends on indexed fields.

For example, in my table Users every user has unique varchar(20) field - login, and primary key - id.

And "Select * from users" returns rowset ordered by login.