Calculating point layer values within polygon features in QGIS 2

Question

There are two layers

• polygon 'BereichBerechnung' with a field "Are_Number"
• points 'EW2017' with a field "EWjeAdr"

In QGIS with a Virtual Layer, I want to calculate the sum of the field "EWjeAdr" for points that are within each feature from the layer 'BereichBerechnung'.

I have found Updating field to give count of points in polygon using STIntersects? which seems related but I cannot figure out how to adjust my expression properly.

With this code:

SELECT Are_Number, SUM(EWjeAdr)
FROM BereichBerechnung
JOIN EW_Data ON BereichBerechnung.ogr_geometry.STContains(EW2017.ogr_geometry) = 1;
GROUP BY Are_Number

I am getting the following error:

How can I do it?

Answer 1

With a bit of luck and suggestions from @Kazuhito, I ended up with

SELECT ST_UNION(B.geometry), B."Are_Number", SUM(D."EWjeAdr")
FROM "BereichBerechnung" AS B
JOIN "EW_Data" AS D ON contains(B.geometry, D.geometry)
GROUP BY B."Are_Number"

In case if there is a necessity to preserve geometries for which there are no overlaps between polygons and points in other words contains(B.geometry, D.geometry) command gives NULL use LEFT JOIN which will do the trick.

SELECT ST_UNION(B.geometry), B."Are_Number", SUM(D."EWjeAdr")
FROM "BereichBerechnung" AS B
LEFT JOIN "EW_Data" AS D ON contains(B.geometry, D.geometry)
GROUP BY B."Are_Number"

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References:

• PostGIS view has missing features
• SpatiaLite SQL functions reference list

Answer 2

For QGIS 3

In the Processing Toolbox use the tool "Join attributes by location (summary)", make sure it's the summary tool and not the other one.

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For QGIS 2

In the Processing Toolbox use the tool "Join attributes by location" and change the Attribute summary option to Take summary of intersecting features.

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The Input layer should be the polygon and the Join Layer should be the points.

I created two scratch layers in a project, in the point layer I populated a field with a random number ("rand_num"), see the result of the joined polygon here: