NLS_CHARSET_NAME returns the name corresponding to a specified character set number.
charset_id is a valid character set number or one of these keywords:
CHAR_CS represents the database character set.
NCHAR_CS represents the national character set. The national character set for the database can be either UTF-8 or AL16UTF16 (default). However, the national character set for analytic workspaces is always UTF-8.
If the number does not correspond to a character set, then the function returns NULL.
NLS_CHARSET_NAME(2000) returns the value