How to add a geometry to an existing feature that was created with NULL geometry?

Question

I have a simple SpatiaLite geodb loaded in QGIS with one table. There is a POINT geometry field and some alphanumeric data. In some cases I can record data about a specific site, but the coordinates are not available at this time and will be retrieved and recorded later. In some other cases I have the coordinates and I want to insert them right into the geometry field, preferably by clicking on the map canvas in the same way available for adding new features (having a separate text field for the coordinates and generating the geometry from that is a no-go).

How do I add a geometry to an existing feature that was created with a NULL geometry field?

Answer 1

If you're after a GUI solution, you can use the "Add Part" tool (QGIS >=2.2 only). First, make your layer editable. Then in an Attribute Table select a single row with a null geometry that you want to add a geometry to. Back in the map canvas, select the "Add Part" tool and draw your geometry. The null geometry will be replaced by your newly drawn shape.

Answer 2

You can do this straight in spatialite. Run an UPDATE query each time you have the coordinates available like:

UPDATE point_table 
SET geometry=MakePoint(<your_new_x_coord>,<your_new_y_coord>, SRID)   
WHERE site_id=...;

This can be done from the spatialite_gui, or one of the QGIS database plugins. Does that help?