Oracle this month, last month, last year

select trunc(sysdate, ‘month‘ ) 本月第一天,         trunc(last_day(sysdate)) 本月最后一天,         trunc(add_months(sysdate, -1), ‘month‘ ) 上月第一天,         trunc(last_day(add_months(sysdate, -1))) 上月最后一天,         trunc(add_months(sysdate, -12), ‘month‘ ) 去年本月第一天,         trunc(last_day(add_months(sysdate, -12))) 去年本月最后一天    from dual

Add_month (date, number) Use the date inside the month plus number to get a new date, if the number is negative you can get past month date last_day (date) Get the last day of the month

This is going to use the add_months () function parameter negative to represent the forward  positive representation of the future.
Select To_char (Add_months (Trunc (sysdate), -1), ' Yyyymm ') from dual;
--Last one months
Select To_char (Add_months (Trunc (sysdate), 1), ' Yyyymm ') from dual;
--Next one months

Oracle this month, last month, last year