Bounding box extent

extent(box) → box

WITH boxes(b) AS (
  SELECT tbox 'TBOXFLOAT XT((1,3),[2001-01-01,2001-01-03])' UNION
  SELECT tbox 'TBOXFLOAT XT((5,7),[2001-01-05,2001-01-07])' UNION
  SELECT tbox 'TBOXFLOAT XT((6,8),[2001-01-06,2001-01-08])'
)
SELECT extent(b) FROM boxes;
-- TBOXFLOAT XT((1,8),[2001-01-01,2001-01-08])
WITH boxes(b) AS (
  SELECT stbox 'STBOX Z((1,1,1),(3,3,3))' UNION
  SELECT stbox 'STBOX Z((5,5,5),(7,7,7))' UNION
  SELECT stbox 'STBOX Z((6,6,6),(8,8,8))'
)
SELECT extent(b) FROM boxes;
-- STBOX Z((1,1,1),(8,8,8))