Loading Well-Known-Text (WKT) using ST_PointFromText, ST_LineFromText, ST_MPointFromText, MLineFromText, MPolyFromText, PolyFromText
Syntax: ST_PointFromText(wkt representation, SRID)
PointFromText(wkt representation) Note the versions that don't take an SRID return unprojectable geometries so should probably be avoided
Note: Beginning with 1.2.1+ - the names without the ST_ prefix are preferred over the non-ST prefixed ones to conform to newer OGC standards. In future releases the non-ST names will be deprecated and eventually removed from PostGIS.
ST_PointFromText (previously known as PointFromText) and ST_LineFromText (previously known as LineFromText) and the other <Geometry Type>FromText functions are very similar to the all-purpose ST_GeomFromText, except that PointFromText only converts Point WKT geometry representations to a geometry object and returns null if another kind of Geometry is passed in. LineFromText similarly only converts WKT representations of Lines to geometry and returns null if another WKT representation is passed in.
If you look at the current underlying implementation of these functions in PostGIS (1.2.1 and below), you will observe that they in fact call ST_GeomFromText, but if the geometry type of the generated geometry is not a Point or a LineString respectively, then the functions return null.
The M*FromText, ST_M*FromText functions create Multi geometry types from the WKT representation of those types.
Since these function do have some added overhead (not much but some), it makes sense to just use ST_GeomFromText unless you have a mixed bag of WKT geometries coming in and only wish to selectively insert say the Points or the Lines or if just for plain readability to make it clear that you are indeed inserting Points or lines or MultiLineStrings etc.
SET thepoint_lonlat = PointFromText('POINT(' || longitude || ' ' || latitude || ')',4326)
Post Comments About PointFromText, LineFromText, ST_PointFromText, ST_LineFromText OGC functions - PostGIS