I have a database with various defined polygons which represent the outer boundarys of buildings on a map of a business park.
If I perform a Select within Management Studio, I get a result similar to the following:
LocationCode LocationPolygon
1 POLYGON((1 1, 2 1, 2 2, 1 2, 1 1))
2 POLYGON((10 10, 20 10, 20 20, 10 20, 10 10))
What I would like to get is the following:
LocationCode PointX PointY
1 1 1
1 2 1
1 2 2
1 1 2
2 10 10
etc etc etc
I cannot see anywhere where I can extract the points from the Polygon using SQL Server from within a SQL Query? I can evidentally take the whole polygon and then do the rest on the client, but I would rather deal in SQL if possible.
Any help appreciated in pointing me in the right direction.
I've answered a similar question before and that time I used a user defined function to extract the points and return a table. Assuming a table Locations
defined as: (LocationCode int, LocationPolygon geometry)
then the following function:
CREATE FUNCTION dbo.GetPoints()
RETURNS @ret TABLE (LocationCode INT, PointX INT, PointY INT)
AS
BEGIN
DECLARE @max INT
SET @max = (SELECT MAX(LocationPolygon.STNumPoints()) FROM Locations)
;WITH Sequence(Number) AS
(
SELECT 1 AS Number
UNION ALL
SELECT Number + 1
FROM Sequence
WHERE Number < @max
)
INSERT INTO @ret
SELECT
l.LocationCode
,l.LocationPolygon.STPointN(nums.number).STX AS PointX
,l.LocationPolygon.STPointN(nums.number).STY AS PointY
FROM Locations l, Sequence nums
WHERE nums.number <= l.LocationPolygon.STNumPoints()
RETURN
END;
When executed as SELECT DISTINCT * FROM dbo.GetPoints() ORDER BY LocationCode;
will give the following result (using your sample data):
| LOCATIONCODE | POINTX | POINTY |
|--------------|--------|--------|
| 1 | 1 | 1 |
| 1 | 1 | 2 |
| 1 | 2 | 1 |
| 1 | 2 | 2 |
| 2 | 10 | 10 |
| 2 | 10 | 20 |
| 2 | 20 | 10 |
| 2 | 20 | 20 |
I'm sure the function can be improved, but it should give you some ideas on how this problem can be solved.