select * from V$NLS_PARAMETERS;
SQL> alter session set NLS_DATE_LANGUAGE = SIMPLIFIED CHINESE;
Session altered
SQL> Select to_char(sysdate,yyyy-Mon-day) from dual;
TO_CHAR(SYSDATE,YYYY-MON-DAY
------------------------------
2009-5月 -星期三
SQL> alter session set NLS_DATE_LANGUAGE=AMERICAN;
Session altered
SQL> Select to_char(sysdate,yyyy-Mon-day) from dual;
TO_CHAR(SYSDATE,YYYY-MON-DAY
------------------------------
2009-May-wednesday
SQL>