STMulti — Function that returns @p_geometry as a MULTI* geometry
Function [dbo].[STMulti] ( @p_geometry geometry ) Returns geometry
In situations where a geometry column is constrained to hold only the multi version of a base geometry, storage of a single geometry eg LineString requires that geometry to be wrapped as a multi geometry eg MultiLineString.
ALTER TABLE [dbo].[Colony] WITH CHECK
ADD CONSTRAINT [Colony_Geom_Geometry_Type_Ck]
CHECK ([geom] is null OR [geom].[STGeometryType]()=’MultiPoint’);
So, @p_geometry is returned as a MULTI* geometry, e.g., POINT -> MULTIPOINT
If @p_geometry is already a MULTI*, it is returned unchanged e.g., MULTIPOINT -> MULTIPOINT
STMulti, where is wraps the single geometry returns a multi-geometry that contains only 1 geometry, so the SQL Server Spatial function STNumGeometries will return 1.
@p_geometry (geometry) - Supplied geometry of a supported type.
This function always returns a multi-geometry type object.
A CircularString input geometry is returned as a GEOMETRYCOLLECTION as it cannot be returned as a MUTLICURVE as it is not instantiable.
Additionally, one cannot construct a MULTILINESTRING containing it MUTLILINESTRING(CIRCULARSTRING(….)).
CompoundCurves are not supported because MultiCurve is not instantiable in SQL Server Spatial
USE GISDB -- Change to your own database. GO SELECT f.mGeom.AsTextZM() as mGeom, f.mGeom.STNumGeometries() as numGeometries FROM (SELECT [dbo].[STMulti](geometry::STPointFromText('POINT(0 0)',0)) as mGeom UNION ALL SELECT [dbo].[STMulti](geometry::STGeomFromText ('POLYGON ((0 0,10 0,10 10,0 10,0 0))',0)) as mgeom UNION ALL SELECT [dbo].[STMulti](geometry::STGeomFromText ('LINESTRING(0 0,10 10,20 20)',0)) as mgeom UNION ALL SELECT [dbo].[STMulti](geometry::STGeomFromText('CIRCULARSTRING(9.962 -0.872,10.1 0,9.962 0.872)',0)) as mgeom ) as f; GO mGeom numGeometries MULTIPOINT ((0 0)) 1 MULTIPOLYGON (((0 0, 10 0, 10 10, 0 10, 0 0))) 1 MULTILINESTRING ((0 0, 10 10, 20 20)) 1 GEOMETRYCOLLECTION (CIRCULARSTRING (9.962 -0.872, 10.1 0, 9.962 0.872)) 1
I hope this function is of use to someone.