Character set in Oracle

show database's character set used in datafile.

SELECT * FROM v$nls_parameters
WHERE parameter = 'NLS_CHARACTERSET';

or

SELECt * FROM nls_database_pramaters
WHERE parameter = 'NLS_CHARACTERSET';

set client character set
#以下の例は日本語のShiftJISを使用する

NLS_LANG=Japanese_Japan.JA16SJIS