Question

I need to calculate the are of overlap between polygons in the same table. Idealy I would like to use mssql spatial capabilities for this (something like @a.SHAPe.STIntersections(@b.SHAPE).STArea()).

But I do not know how to do this for polygons in the same layer.

Thanks!

Freddie

Answer 1

I have knock up a little example for you that shows you how this can be accomplished.

SELECT 

    a.Geog1.STIntersection(b.Geog2) AS OverlapGeog
,   a.Geog1.STIntersection(b.Geog2).STArea() AS AreaOverlap
FROM
(
    SELECT 
    GEOGRAPHY::STGeomFromText('POINT(0.0 0.0)',4326).STBuffer(100) AS Geog1
) a
INNER JOIN
(
    SELECT 
    GEOGRAPHY::STGeomFromText('POINT(0.001 0.0)',4326).STBuffer(100) AS Geog2
) b
On
a.Geog1.STIntersects(b.Geog2) = 1