[Qgis-user] Request methods

[Mathieu Gillot]

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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