2

For example, I have two layers:

  • A polygon layer city block with a ID field city block index.
  • A point layer parking lot with a field parking lot size.

I want to know the total parking lot size for each feature in the land use layer, so I use the spatial join function. Here's my workflow:

  1. Use join attributes by location (summary) to create a new temporary joined layer who contains a field called parking lot size_sum.
  2. Go to the property panel of the city block layer and join the parking lot size_sum field as a new field called joined layer_parking lot size_sum.
  3. In the city block layer, create a new field called total parking lot size .
  4. Copy values from joined layer_parking lot size_sum and paste them into total parking lot size.
  5. Delete the temporary joined layer.

All I want to do is to add a new field into the original city block layer by summarizing the parking lot size field. But I have to go through all the steps above. Is there a simpler way to do that?

Improve this question
0

1 Answer 1

Reset to default
3

There is a possibility using a "Virtual Layer" through Layer > Add Layer > Add/Edit Virtual Layer...

With the following Query, it is possible to know the total 'parking lot size' for each 'city block'.

SELECT cb.*, SUM(pl."parking lot size") AS pl_sum
FROM "city block" AS cb
JOIN "parking lot" AS pl ON st_contains(cb.geometry, pl.geometry)
GROUP BY cb."city block index"
Improve this answer
4
  • Thanks. I can't quite differentiate whether it's the layer name or the field name each name in your answer refers to. So I differentiate them a little bit in my question. Could you please also update your answer accordingly? Commented Aug 25, 2020 at 9:34
  • Please check updates Commented Aug 25, 2020 at 11:39
  • Thanks! It helps. Though, I guess you made a typo by typing pl as pls in the first line. Also, it seems that a virtual layer has a performance issue compared to a regular layer. It takes much more longer time to respond for each of my operations, like panning or opening the attribute table. Commented Aug 27, 2020 at 9:34
  • 1
    you are right. And yes the performance of VLs is not their best quality. Commented Aug 27, 2020 at 15:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.