I have a layer my_layer
containing a virtual field virtual_1
. Next step I want to create a virtual layer, which list only unique values (as a bonus also dissolves the geometries by unique values).
The following query for the virtual layer doesn't work with virtual fields:
SELECT DISTINCT virtual_1 from my_layer
How could the desired outcome be achieved?
Some notes/ideas:
- I need an dynamic solution, as the data in
my_layer
gets updated reguarly. So unfortunately the Vector>Analysis>Unique Values isn't an option. Also Dissolving by virtual field is therefore not an option. - Would it work to generate the virtual field inside the query itself? How could an expression of the field editor evaluated in the virtual-field-query?