Lan,
Beside Tom's comments, you won't be allowed to drop the database while you are working on it.
(no drop database will succceed if users are still working). So, connect to template1 and fire the SQL with the quotes (dixit Tom Lane) or just use the dropdb command line tool
SCM=# drop database SCM;
ERROR: database "scm" does not exist
Regards,
Guido Barosio
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