GEOGRAPHY_LENGTH
This function measures the length of a path or the total perimeter of a polygon, in meters.

Syntax
GEOGRAPHY_LENGTH ( geo )
Arguments
geo: any valid geospatial object or WKT string: path, point or polygon.
Return Type
Double. In the case of a POINT, the length is always 0.
Examples
SELECT ROUND(geography_length(shape), 0) AS perimeter FROM neighborhoods; **** +-----------+ | perimeter | +-----------+ | 8558 | | 9188 | | 4831 | | 11990 | | 9455 | | 7886 | | 6418 | | 8580 | | 7983 | +-----------+