This may be a silly question but I don't see any place where the documentation explicitly addresses whether or not you can designate a particular column as a primary key after the table is created. I used the "create table as " syntax to create a table with the same columns as an original table, but I want to rename id column, make it a serial, and designate it as a primary key. Is it possible to do this? I've tried a number of things to do this and none of them have worked.