Find First and Last Day of the last Quarter in ORACLE

This one is simpler, but may still be not the simplest way:

SELECT
  ADD_MONTHS(TRUNC(SYSDATE, 'Q'), -3) AS First,
  TRUNC(SYSDATE, 'Q') - 1 AS Last
FROM DUAL

Maybe you could also use a subselect, like this, to exclude some repetition of code:

SELECT
  ADD_MONTHS(D, -3) AS First,
  D - 1 AS Last
FROM (SELECT TRUNC(SYSDATE, 'Q') AS D FROM DUAL)

SELECT
  TRUNC(SYSDATE, 'Q')AS FIRST_DAY,
  last_day(add_months(TRUNC(SYSDATE, 'Q'),2)) as LAST_DAY                
FROM DUAL;

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