SQL SELECT PRIMER Y ULTIMO DIA DE MES ACTUAL Y ANTERIOR

select
trunc( sysdate ,'MM') "primer día de este mes",
LAST_DAY(sysdate) "ultimo día de este actual",
to_number(to_char( trunc(add_months(sysdate,-1) ,'MM'),'dd')),
to_number(to_char( trunc(add_months(sysdate,-1) ,'MM') ,'mm')),
to_number(to_char( trunc(add_months(sysdate,-1) ,'MM') ,'yy')),
trunc( add_months(sysdate,-1) ,'MM')   "priemr dia del mes pasado",
LAST_DAY( add_months(sysdate,-1)  ) "ultimo dia mes pasado",
to_number(to_char( LAST_DAY(sysdate)-1 , 'dd')) ,
to_number(to_char( LAST_DAY(sysdate)-1 , 'mm')),
to_number(to_char( LAST_DAY(sysdate)-1 , 'yy'))
from dual;