Find Oracle Database Character Set

Character Sets
(Ordinary) character set
The (ordinary) character set for a database can be determined with:

SQL> select value from nls_database_parameters where parameter = 'NLS_CHARACTERSET';

National character set
The national character set for a database can be determined with:

SQL> select value from nls_database_parameters
where parameter = 'NLS_NCHAR_CHARACTERSET';