Generates a table with dates

days.sql

-- Generates a table with dates, 
-- "duration" - number of days
-- "days_ago" - start day
WITH params AS (SELECT
                    40 AS days_ago,
                    10 AS duration
                FROM dual)
SELECT
    LEVEL,
    to_date(to_char(SYSDATE - LEVEL - params.days_ago, 'DD-MM-YYYY'), 'DD-MM-YYYY')
FROM DUAL, params
CONNECT BY LEVEL <= params.duration;