-- set language
alter session set nls_language ='AMERICAN';
alter session set nls_language = 'SIMPLIFIED CHINESE';

-- set date language
alter session set nls_date_language='AMERICAN';
alter session set nls_date_language='SIMPLIFIED CHINESE';

-- view session nls_language
select USERENV('LANG') from DUAL;

-- view session nls_date_language
select SYS_CONTEXT('USERENV','NLS_DATE_LANGUAGE') nls_date_language from DUAL;