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    STGeometryTypes: Extracting all geometry type string values from complex geometry
    STDensify: Densify (m)LineString or (m)Polygon geometry objects
    STInsertN: Insert single vertex into a geometry
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    STUpdate: Replace all points equal to the supplied point with replacement point.
    STDeleteN: Delete single vertex from geometry
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    STFlipVectors: Normalize direction of linestring vectors
    STConvertToLineString: Extract LineStrings in GeometryCollection to create LineString
    STLine2Cogo: Converting LineStrings to COGO XML
    STCogo2Line: Creating (Multi)LineStrings geometries from COGO XML instructions
    STVectorize: Break Linestring/Polygon elements into 2 point vectors (or 3 point circular curves)
    STScale: Function to Scale a geometry object
    TSQL String Tokenizer Function for SQL Server
    STGeometry2MBR/STGeography2MBR: Compute and return MBR ordinates
    generate_series for SQL Server 2008
    STExtractPolygon: Extract Polygons from result of STIntersection in SQL Server Spatial
    STRound: Function to round ordinates of a SQL Server Spatial geometry object
    STExtract: Extract elements of a geometry object
    STNumRings: Counting number of polygon rings
    STFilterRings: Removing rings from Polygon based on area.
    STMove: Function to Move a geometry object in SQL Server Spatial
    STCentroid*: Alternate Functions for Compute a Centroid
    STRotate: Function to rotate a geometry object in SQL Server Spatial
    STVertices: Wrapper over STDumpPoints
    STMorton: Creating a Morton number Space Key value for grid square
    Gridding a geometry or geography object (SQL Server Denali)
    On hinting spatial indexes
    RandomSearchByExtent: Random Search Procedure (2008 Spatial)
    COGO: Convert DMS String to decimal degrees floating point number.
    COGO: Converting (Google Earth) Formatted Longitude/Latitude points to decimal degrees (SQL Server)
    COGO: Convert Degrees, Minutes and Seconds values to Decimal Degrees
    COGO: DD2DMS Formatting a latitude/longitude decimal degree value
    COGO: Create point from bearing and distance
    COGO: Compute number of vertices required to stroke circle or circular arc
    COGO: Calculating the bearing between two points (SQL Server 2008 Spatial)
    COGO: Compute arc length subtended by angle centre of circle
    COGO: Compute chord length of segment of a circle (arc)
    COGO: Computing Arc To Chord (Arc2Chord) Separation
    COGO: Creating a stroked polygon from a circle's centre x,y and radius
    COGO: Finding centre and radius of a curve defined by three points: FindCircle function
    CheckRadii: Identifying Tight Radius Curves sections within LineString geometry data
    Generating random point data for SQL Server 2008 Spatial
    New Presentation on Active (Searchable) Spatial Metadata for SQL Server 2008 Spatial and FreeText
    STisGeo: Checking if a column in a table or a view is of type geometry or geography
    Vectorising geometry objects in SQL Server 2008
    STMBR2Geometry/STMBR2Geography functions
    Extracting geometry types from geometry/geography objects in SQL Server 2008
    Getting the number of coordinate dimensions of a geometry/geography object in SQL Server 2008
    STDumpPoints: A Function that Dumps the Vertices/Points in a geometry
    toGeography and toGeography Conversion Functions for SQL Server 2008 Spatial
    Write text file with spatial data from SQL Server 2008
    Loading Shapefiles into Geography type column in SQL Server 2008
    Tip #6: Correcting invalid geometries
    Tip #5: Where or where has my little column gone
    Tip #4: What Coordinate System is that?
    Tip #3: What object is that?
    Tip #2: Spatial Indexing and Primary Keys
    Tip #1: SQL Server 2008 "Katmai" - Setting SRIDs

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All Blog Articles, Data Models and Free Source Code by Simon Greener, The SpatialDB Advisor is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

STNumRings: Counting number of polygon rings

Monday January 02 2012 at 03:37

Keywordscount rings polygon multipolygon sql server spatial inner outer
Summary

This article presents a simple wrapper function that allows one to count the number of inner and outer rings of a polygon or multipolygon geometry via a single call.

Here is an “ease of use” function that allows you to count the number of rings of a polygon or multipolygon geometry object in SQL Server Spatial.

  1. USE [GISDB] -- Change this to your database
  2. GO
  3. -- Function: STNumRings
  4. --
  5. CREATE FUNCTION dbo.STNumRings(@p_geometry geometry)
  6. RETURNS INT
  7. AS
  8. BEGIN
  9.   DECLARE
  10.     @v_GeometryType VARCHAR(1000),
  11.     @v_geom         geometry,
  12.     @v_geomn        INT = 0,
  13.     @v_ringn        INT = 0;
  14.   BEGIN
  15.     IF ( @p_geometry IS NULL )
  16.        RETURN 0;
  17.     SET @v_GeometryType = @p_geometry.STGeometryType();
  18.     IF ( @v_GeometryType IN ('Point','MultiPoint','LineString','MultiLineString' ) )
  19.        RETURN 0;
  20.     IF ( @v_GeometryType IN ('Polygon','CurvePolygon') )
  21.     BEGIN
  22.       SET @v_ringn = 1 + @p_geometry.STNumInteriorRing();
  23.     END;
  24.     IF ( @v_GeometryType = 'MultiPolygon' )
  25.     BEGIN
  26.       SET @v_geomn  = 1;
  27.       WHILE ( @v_geomn <= @p_geometry.STNumGeometries() )
  28.       BEGIN
  29.         SET @v_geom  = @p_geometry.STGeometryN(@v_geomn);
  30.         SET @v_ringn = @v_ringn + 1 + @v_geom.STNumInteriorRing();
  31.         SET @v_geomn = @v_geomn + 1;
  32.       END;
  33.     END;
  34.     IF ( @v_GeometryType = 'GeometryCollection' )
  35.     BEGIN
  36.       SET @v_geomn  = 1;
  37.       WHILE ( @v_geomn <= @p_geometry.STNumGeometries() )
  38.       BEGIN
  39.          SET @v_ringn = @v_ringn + dbo.STNumRings(@p_geometry.STGeometryN(@v_geomn));
  40.          SET @v_geomn = @v_geomn + 1;
  41.       END;
  42.     END;
  43.     RETURN @v_ringn;
  44.   END;
  45. END
  46. GO

Some tests.

  1. SELECT 'Point' AS gtype, dbo.STNumRings(geometry::STGeomFromText('POINT(0 0)',0)) AS numRings
  2. UNION ALL
  3. SELECT 'MultiPoint' AS gtype, dbo.STNumRings(geometry::STGeomFromText('MULTIPOINT((0 0),(20 0))',0)) AS numRings
  4. UNION ALL
  5. SELECT 'LineString' AS gtype, dbo.STNumRings(geometry::STGeomFromText('LINESTRING(0 0,20 0,20 20,0 20,0 0)',0)) AS numRings
  6. UNION ALL
  7. SELECT 'MultiLineString' AS gtype, dbo.STNumRings(geometry::STGeomFromText('MULTILINESTRING((0 0,20 0,20 20,0 20,0 0),(10 10,10 11,11 11,11 10,10 10),(5 5,5 7,7 7,7 5,5 5))',0)) AS numRings
  8. UNION ALL
  9. SELECT 'Polygon Outer' AS gtype, dbo.STNumRings(geometry::STGeomFromText('POLYGON((0 0,20 0,20 20,0 20,0 0))',0)) AS numRings
  10. UNION ALL
  11. SELECT 'Polygon' AS gtype, dbo.STNumRings(geometry::STGeomFromText('POLYGON((0 0,20 0,20 20,0 20,0 0),(10 10,10 11,11 11,11 10,10 10),(5 5,5 7,7 7,7 5,5 5))',0)) AS numRings
  12. UNION ALL
  13. SELECT 'MultiPolygon' AS gtype, dbo.STNumRings(geometry::STGeomFromText('MULTIPOLYGON (((0 0,20 0,20 20,0 20,0 0),(10 10,10 11,11 11,11 10,10 10),(5 5,5 7,7 7,7 5,5 5)), ((80 80, 100 80, 100 100, 80 100, 80 80)), ((110 110, 150 110, 150 150, 110 150, 110 110)))',0)) AS numRings
  14. UNION ALL
  15. SELECT 'CurvePolygon' AS gtype, dbo.STNumRings(geometry::STGeomFromText('CURVEPOLYGON(COMPOUNDCURVE((0 -23.43778, 0 23.43778),CIRCULARSTRING(0 23.43778, -45 23.43778, -90 23.43778),(-90 23.43778, -90 -23.43778),CIRCULARSTRING(-90 -23.43778, -45 -23.43778, 0 -23.43778)))',0)) AS numRings
  16. UNION ALL
  17. SELECT 'GeometryCollection' AS gtype, dbo.STNumRings(geometry::STGeomFromText('GEOMETRYCOLLECTION(CURVEPOLYGON(COMPOUNDCURVE((0 -23.43778, 0 23.43778),CIRCULARSTRING(0 23.43778, -45 23.43778, -90 23.43778),(-90 23.43778, -90 -23.43778),CIRCULARSTRING(-90 -23.43778, -45 -23.43778, 0 -23.43778))), COMPOUNDCURVE(CIRCULARSTRING(-90 -23.43778, -45 -23.43778, 0 -23.43778), (0 -23.43778, 0 23.43778)))',0)) AS numRings;

Resulting in:

gtype numRings
Point 0
MultiPoint 0
LineString 0
MultiLineString 0
Polygon Outer 1
Polygon 3
MultiPolygon 5
CurvePolygon 1
GeometryCollection 1

I hope this is useful to someone.

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