Come ottenere il primo e l'ultimo giorno della settimana in Oracle?

SETTIMANA

select TRUNC(sysdate, 'iw') AS iso_week_start_date,
       TRUNC(sysdate, 'iw') + 7 - 1/86400 AS iso_week_end_date
from dual;

MESE

select 
TRUNC (sysdate, 'mm') AS month_start_date,
LAST_DAY (TRUNC (sysdate, 'mm')) + 1 - 1/86400 AS month_end_date
from dual;