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.


Eigenshaften > Verknüpfungen, add the attribute files and select theIDfields to join with the relevant field from the source layer. Once done, open the Attribute Table for your source layer, click the bottom-left button and selectFortgeschrittener Filterand use an expression like"ID" = 3 AND "Date" = '2014-01-01'. – Joseph May 18 '16 at 09:58