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I have one source shapefile like this: It consist the geographical coordinates of weather stations:
And several attribute files, which contain the Temperature data of each date for several years
I managed to linked them through the ID (project properties/ Relations).
Now I want to access for example the Temperature from the weather station 3 at a specific date. With the attribute table I can see all the values, but I don't know how to query some values with the Field Calculator. I can’t access the linked data.