PQftable insufficient for primary key determination

Imagine i have a table A with primary key "p" and another attribute called "data":

SELECT * from A, A, B;

here, i will have 2 columns "data", PQftable tells me that they are from A, but
which of the 2 columns "p" is the primary key of the tuple (of the table A)?

Is it possible to get distinguish the 2 instances of the table A?