-- First day of month
SELECT TRUNC(sysdate, 'MONTH') from dual;
-- Oracle: First day of year
SELECT TRUNC(sysdate, 'YEAR') FROM DUAL;
-- trunc(date, format) DUAL is for Oracle
SELECT trunc(sysdate, 'Q') FROM DUAL; -- 1rst quarter day
SELECT trunc(sysdate) FROM DUAL; -- today 00:00:00
SELECT trunc(sysdate, 'YEAR') FROM DUAL; -- 1rst year day
SELECT trunc(sysdate, 'MONTH') FROM DUAL; -- 1rst month day