Okay, time to wrap things up! What did we learn?

1. You can add a UNIQUE constraint to a single column, placing it after the column type:

   CREATE TABLE board_game (
     id integer PRIMARY KEY,
     name varchar(32) UNIQUE
   );

2. You can add a UNIQUE constraint to a group of columns, placing it after the column definitions:

   CREATE TABLE board_game (
     id integer PRIMARY KEY,
     name varchar(32),
     genre varchar(32),
     UNIQUE (name, genre)
   );

3. You can add a UNIQUE constraint to an existing table:

   ALTER TABLE video_game
   ADD CONSTRAINT video_game_unique UNIQUE (name, platform);

4. You can remove a UNIQUE constraint from an existing table:

   ALTER TABLE group_game
   DROP CONSTRAINT group_game_name_key;

How about a quick quiz now?