ST_MaxDistance

Introduction: Calculates and returns the length value representing the maximum distance between any two points across the input geometries. This function is an alias for ST_LongestDistance.

Format: ST_MaxDistance(geom1: Geometry, geom2: Geometry)

SQL Example:

SELECT ST_MaxDistance(
        ST_GeomFromText("POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))"),
        ST_GeomFromText("POLYGON ((10 20, 30 30, 40 20, 30 10, 10 20))")
)

Output:

36.05551275463989