NLS_CHARSET_NAME returns the name of the character set corresponding to ID number
number. The character set name is returned as a
VARCHAR2 value in the database character set.
number is not recognized as a valid character set ID, then this function returns null.
The following example returns the character set corresponding to character set ID number 2:
SELECT NLS_CHARSET_NAME(2) FROM DUAL; NLS_CH ------ WE8DEC