ST_BoundingDiagonal

Introduction: Returns a linestring spanning minimum and maximum values of each dimension of the given geometry's coordinates as its start and end point respectively. If an empty geometry is provided, the returned LineString is also empty. If a single vertex (POINT) is provided, the returned LineString has both the start and end points same as the points coordinates

Format: ST_BoundingDiagonal(geom: Geometry)

SQL Example:

SELECT ST_BoundingDiagonal(ST_GeomFromWKT(geom))

Input: POLYGON ((1 1 1, 3 3 3, 0 1 4, 4 4 0, 1 1 1))

Output: LINESTRING Z(0 1 1, 4 4 4)

Input: POINT (10 10)

Output: LINESTRING (10 10, 10 10)

Input: GEOMETRYCOLLECTION(POLYGON ((5 5 5, -1 2 3, -1 -1 0, 5 5 5)), POINT (10 3 3))

Output: LINESTRING Z(-1 -1 0, 10 5 5)