Query a select that returns all the fields of an specific value of primary key without knownig the name of the single column's primary key?

Hi!
I need to query a select that returns all the fields of an specific primary key, but I don't have the  single column's name that is constrained as primary key.
How can I do that?
Something like:
SELECT * FROM myTable WHERE myTable.pkey = 'foo';

Thanks
Carlos Henrique Iazzetti Santos
Compels Informática
Santa Rita do Sapucaí - MG
www.compels.net