When I set up a table join in one layer A, how do I find all elements from layer B that didn't find their way into the joined table?
This is much like doing a left outer join and trying to find all elements from the right table (B above) that didn't go into the join.
I suppose I should be able to set up a join in layer B and use layer A as the lookup table. Then, I could just mark all elements with NULL values in the joined fields, but somehow, QGIS won't let me set up a join in layer B for layer A. Which is really strange.
Layer A has 5000+ features. Layer B has 280 features.
When I inspect the attribute table for layer A and sort layer A by an identifier of layer B, I get 268 joined elements. OK, I have 12 elements in layer B without a match. Of course, since they don't appear in the joined attribute table, I would need to look for them in layer B. But in layer B, of course, they are unmarked.
Setting up a join in layer B properties for layer A doesn't work (the join settings window remains blank after setting up the join). Well, then I tried "join by attribute" and did not skip the faulty output, which I saved as separate layer. This layer should have 12 elements, but only has 10. I must be doing something wrong. How would you find the unjoinable features in layer B?