Select a part from the daterange column type

Question

Maybe there is a function?

SELECT min('[2010-01-01, 2010-02-01)'::daterange); Should return: '2010-01-01'

SELECT max('[2010-01-01, 2010-02-01)'::daterange); Should return: '2010-01-31'

Answer 1

No, but you could use upper_inc, upper, lower_inc, lower functions to write such a function:

WITH dr AS (
  SELECT '[2010-01-01, 2010-02-01)'::daterange r
), t AS (
  SELECT r, lower_inc(r) li, upper_inc(r) ui, lower(r) l, upper(r) u FROM dr
)
SELECT CASE WHEN li THEN l ELSE l + INTERVAL '1 DAY' END AS "range_minimum"
     , CASE WHEN ui THEN u ELSE u - INTERVAL '1 DAY' END AS "range_maximum"
FROM t;