Common point in multiple polygons in SQL - sql

Question

i have two tables that contains a list geometry data
Ex. (0xE6100000010CFB24190B88E44A40AADDAB69817F3740)
i did the intersection of shapes between the two tables , now i'm trying to find a common point in all the intersected shapes
i tried to find the STCentroid() of each shape , but i can't find out how to find the common point in all of them
select p1.shape_data.STIntersection(p2.shape_data).STCentroid() as inter_geometry
from map_shapes p1
inner join areas_map_shapes p2 on p2.shape_data.STIntersects(p1.shape_data) = 1
where p2.shape_data.STIntersects(p1.shape_data) = 1
and p2.shape_id = 206
i tried also to aggregate all the intersected shapes
SELECT
geometry::UnionAggregate(ss.shape_data),
geometry::STGeomFromText( geometry::UnionAggregate(ss.shape_data).STCentroid().ToString(), 0).STY as lat,
geometry::STGeomFromText( geometry::UnionAggregate(ss.shape_data).STCentroid().ToString(), 0).STX as lon
FROM areas_map_shapes T
inner join map_shapes SS on SS.shape_data.STIntersects(T.shape_data) = 1
WHERE SS.shape_data.STIntersects(T.shape_data) = 1
AND T.shape_id = 206
and T.status = 1
and SS.status = 1
and T.country_id = 4
my problem is that i need to find the only one common point in all the shapes that intersects
adding image to represent what i got so far , this shows all the shapes the intersects with the main shape , i need to find a common point in all of them

Answer 1

Its hard to tell from your example because (as #nbk pointed out) its difficult to reproduce what you're asking for. That said, it looks like you're looking for the STIntersection function.
DECLARE #GeometryTable TABLE(
ID INT,
geom GEOMETRY
)
INSERT INTO #GeometryTable (ID, Geom) VALUES (1, GEOMETRY::STGeomFromText('POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))', 0))
INSERT INTO #GeometryTable (ID, Geom) VALUES (2, GEOMETRY::STGeomFromText('POLYGON((1 1, 1 3, 3 3, 3 1, 1 1))', 0))
INSERT INTO #GeometryTable (ID, Geom) VALUES (3, GEOMETRY::STGeomFromText('POLYGON((0 1, 0 3, 2 3, 2 1, 0 1))', 0))
SELECT
G1.geom.STIntersection(G2.geom).STIntersection(G3.geom)
FROM
#GeometryTable G1
INNER JOIN
#GeometryTable G2
ON
G1.geom.STIntersects(G2.geom) = 1
INNER JOIN
#GeometryTable G3
ON
G1.geom.STIntersects(G3.geom) = 1
AND G2.geom.STIntersects(G3.geom) = 1
WHERE
G1.ID = 1
AND G2.ID = 2
AND G3.ID = 3

Answer 2

Not sure there's an easy/fast way to do it. One idea is to use STIntersection to create a intersection polygon of all your areas in a recursive CTE:
drop table #t_geoms
create table #t_geoms (geom geometry, row_id int identity)
-- create some random data
insert into #t_geoms
select top 30 GEOMETRY::Point(ROW_NUMBER() OVER(ORDER BY object_id) * 0.01 + 10,ROW_NUMBER() OVER(ORDER BY object_id) * 0.01 + 10, 4326).STBuffer(3) x
from sys.objects
;with cte as (
select geom, row_id
from #t_geoms
where row_id = 1
union all
select g.geom.STIntersection(c.geom), g.row_id
from cte c
inner join #t_geoms g
ON g.row_id = c.row_id + 1
)
select top 1 geom, geom.STCentroid() AS centerPointOfIntersection
from cte
order by row_id desc
option(MAXRECURSION 0)
Note that if not all polygons actually intersect, you get an emptry geom