Hello, In my project I need to compare the result of the concatenation of two fields, A and B, in common between two different layers.
For he moment, I'm using a calculated field in each layer to concatenate the two fields. Then a sql request in a virtual layer compare them. Improving my sql abilities, I noticed that I could do that with a single virtual layer and a sql request with two sub requests to concatenate the A and B fields and the primary request to compare them. My question : 1 - what is the more lightweight solution with large sets of data ? I noticed that sql requests could seriously slow down qgis. But calculated fields have to be calculated too... 2 - I do not really master external database solutions yet (I'm using geopackage and project relations between tables). In fine, is a postgresql DB could be a solution in term of velocity ? Are the Qgis VL layers have an equivalent in that kind of database, or must I create them anyway into the SIG ? Thanks for any help. Mathieu G
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