Query execution order

Hi!

I've been playing a bit with my frinends' tables and I wanted to remove an
existing unique constraint and add a primary key with the same name.
However, instead of first removing an existing constraint and then adding a
new one, I added the primary key and then deleted the unique constraint.
When I hit OK I got a pgsql error, telling me that a relation with that
name already exists.

The SQL tag had these queries:
ALTER TABLE uporabniki ADD CONSTRAINT uporabniki_primary_key_key PRIMARY
KEY (primary_key);
ALTER TABLE uporabniki DROP CONSTRAINT uporabniki_primary_key_key;

Is it possible for pgAdmin to reorder the queries so that the drop queries
are first and all the rest follow? Or if it could at least check for
existing constraint names?

Thanks and best regards,
Miha