Databases are destroyed with the command
DROP DATABASE:
DROP DATABASE name;
Only the owner of the database (i.e., the user that created it), or
a superuser, can drop a database. Dropping a database removes all objects
that were
contained within the database. The destruction of a database cannot
be undone.
You cannot execute the DROP DATABASE command
while connected to the victim database. You can, however, be
connected to any other database, including the template1
database.
template1 would be the only option for dropping the last user database of a
given cluster.
For convenience, there is also a shell program to drop
databases:
dropdb dbname
(Unlike createdb, it is not the default action to drop
the database with the current user name.)