Table with no primary key

Good time of the day!

Perhaps it's a stupid question, but I haven't found an answer in the
manual...

It's possible to create a table without setting primary key. So, I
suppose, that Postgresql maintains a kind of internal primary key for
that table.

Questions:
1. Am I right? :)
2. Can I (how?) to access this key?
3. Is this "internal key" maintained for every table or only for those
with no primary key set?


Best regards,
 Dmitri ( mailto:dmitri@listsoft.ru )

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