New To List

Hello All,
   I'm not really sure how joining the list works but I
wanted to say hello. I am new to databases and also to
Postgres. Started reading the book up on the site. Very
helpful.
   I do have a question though. I am trying to take a DB
written for MySql and convert the format of statements
over to Postgres for creation. I can't seem to find a
value 'blob' in PG. Is there something similar?? Also if
anyone can help me with this (see below). I can't figure
out how to make a primary, unique key. Here's the sql
file:
CREATE TABLE session (
   sid varchar(255) NOT NULL,
   val blob NOT NULL,
   changed varchar(14) NOT NULL,
   PRIMARY KEY (sid),
   UNIQUE sid_2 (sid)
);

Again any help or pointers in the right direction is
greatly appreciated.
Kind regards,
Harry Hoffman
Product Systems Specialist
Restaurants Unlimited Inc.
(206) 634-3082 x. 270