How to get the sum of column in two different Layer attributes in QGIS

Question

How do I add the values of a column and then insert it in different table column? e.g. I have a layer1 with attributes as follow:

and layer2 with attributes:

I am trying to sum the MIN with the same ids at layer1 then insert the result in layer2.

Answer 1

There is no GIS-specific aspect to your question, however, if you are using a database like PostGIS with your QGIS you can do the following: (I haven't actually checked if the syntax is correct):

WITH temp AS ( 
SELECT  the_branch, SUM(min)  as min_sum 
FROM layer1 
GROUP BY the_branch) 
UPDATE layer2
SET layer2.total_min=temp.min_sum
FROM temp
WHERE layer1.branch=temp.the_branch;