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Urban Start-up Agglomeration and Venture Capital Investment (view source)
Revision as of 11:50, 26 September 2017
, 11:50, 26 September 2017→GIS Resources
*http://postgis.net/features/
*https://en.wikipedia.org/wiki/GIS_file_formats
====Useful functions for spatial joins====
'''sum(expression)''': aggregate to return a sum for a set of records
'''count(expression)''': aggregate to return the size of a set of records
'''ST_Area(geometry)''' returns the area of the polygons
'''ST_AsText(geometry)''' returns WKT text
'''ST_Buffer(geometry, distance)''': For geometry: Returns a geometry that represents all points whose distance from this Geometry is less than or equal to distance. Calculations are in the Spatial Reference System of this Geometry. For geography: Uses a planar transform wrapper.
'''ST_Contains(geometry A, geometry B)''' returns the true if geometry A contains geometry B
'''ST_Distance(geometry A, geometry B)''' returns the minimum distance between geometry A and geometry B
'''ST_DWithin(geometry A, geometry B, radius)''' returns the true if geometry A is radius distance or less from geometry B
'''ST_GeomFromText(text)''' returns geometry
'''ST_Intersection(geometry A, geometry B)''': Returns a geometry that represents the shared portion of geomA and geomB. The geography implementation does a transform to geometry to do the intersection and then transform back to WGS84
'''ST_Intersects(geometry A, geometry B)''' returns the true if geometry A intersects geometry B
'''ST_Length(linestring)''' returns the length of the linestring
'''ST_Touches(geometry A, geometry B)''' returns the true if the boundary of geometry A touches geometry B
'''ST_Within(geometry A, geometry B)''' returns the true if geometry A is within geometry B
geometry_a '''&&''' geometry_b: Returns TRUE if A’s bounding box overlaps B’s.
geometry_a '''=''' geometry_b: Returns TRUE if A’s bounding box is the same as B’s.
'''ST_SetSRID(geometry, srid)''': Sets the SRID on a geometry to a particular integer value.
'''ST_SRID(geometry)''': Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table.
'''ST_Transform(geometry, srid)''': Returns a new geometry with its coordinates transformed to the SRID referenced by the integer parameter.
'''ST_Union()''': Returns a geometry that represents the point set union of the Geometries.
'''substring(string [from int] [for int])''': PostgreSQL string function to extract substring matching SQL regular expression.
'''ST_Relate(geometry A, geometry B)''': Returns a text string representing the DE9IM relationship between the geometries.
'''ST_GeoHash(geometry A)''': Returns a text string representing the GeoHash of the bounds of the object.
====Native functions for geogrphy====
'''ST_AsText(geography)''' returns text
'''ST_GeographyFromText(text)''' returns geography
'''ST_AsBinary(geography)''' returns bytea
'''ST_GeogFromWKB(bytea)''' returns geography
'''ST_AsSVG(geography)''' returns text
'''ST_AsGML(geography)''' returns text
'''ST_AsKML(geography)''' returns text
'''ST_AsGeoJson(geography)''' returns text
'''ST_Distance(geography, geography)''' returns double
'''ST_DWithin(geography, geography, float8)''' returns boolean
'''ST_Area(geography)''' returns double
'''ST_Length(geography)''' returns double
'''ST_Covers(geography, geography)''' returns boolean
'''ST_CoveredBy(geography, geography)''' returns boolean
'''ST_Intersects(geography, geography)''' returns boolean
'''ST_Buffer(geography, float8)''' returns geography [1]
'''ST_Intersection(geography, geography)''' returns geography [1]
