This is one of the many SQL bad habits you've likely picked up from using MySQL. I'd highly suggest reading the pgsql users manual cover to cover, you'll pick up a lot of good info on how to drive postgresql. Other things that work in mysql but fail in pgsql include inserting things that are out of range.
You know, I bet as many of us came to PostgreSQL from a MySQL background as from Oracle. It might be good to have a section in the manual for how to transition from using the "tricks" in MySQL to a strict environment like Postgres.
