[GIS] Inserting null value into geometry column using PostGIS

postgis

I'm trying to insert a null value into a geometry column, which I cannot do:

ERROR: parse error – invalid geometry

So what I'm trying to accomplish is to erase a point from a map and save that information – the deletion of the point – to the database.

I am new to spatial data and all I can find from the internet is how to insert points, polygons and whatnot, but not how to remove that information.

The table where the geometry column resides has other information as well, so removing a row is not something I can do.

Best Answer

UPDATE "table" SET the_geom = NULL

This will work unless you have a NOT NULL-constraint on the geom-column.

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[GIS] Inserting polygon centroids into an additional column in PostGIS

If you want x and y columns:

ALTER TABLE "test_table" ADD x double precision;
ALTER TABLE "test_table" ADD y double precision;
UPDATE "test_table" SET x = ST_X(ST_Centroid(the_geom));
UPDATE "test_table" SET y = ST_Y(ST_Centroid(the_geom));

If you rather want a geometry column (adjust schema name and CRS to fit your needs):

SELECT AddGeometryColumn ('test_schema','test_table','centroid_geom',4326,'POINT',2);
UPDATE "test_table" SET centroid_geom = ST_Centroid(the_geom);

[GIS] Parse error while inserting values into polygon feature

As commenters point out

You need 4+ points to form a closed polygon
The first and last point must be the same
Polygons can contain multiple rings, so you need two (()) brackets around your exterior ring point list

For example, the unit square

POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))

Best Answer

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[GIS] Inserting polygon centroids into an additional column in PostGIS

[GIS] Parse error while inserting values into polygon feature

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