Check Database Character Set

There are several possible ways to find out the database character set:

select value
from   nls_database_parameters
where  parameter = 'NLS_CHARACTERSET'
;

select property_value
from   database_properties
where  property_name = 'NLS_CHARACTERSET'
;

select value$
from   sys.props$
where  name = 'NLS_CHARACTERSET'
;