5

I have got stuck with a dynamic analysis that I would like to include in a project I am working with. I want to save the query in the project file or make it to a view in my database. I have tried a couple of combination without success so far, but I am on a SQL learning curve =).

I would like to combine the queries below so that my ST_buffer is used in the same query as the layer where building.geom need to be completely inside. Is this possible?

SELECT
    event_point.id,
    event_point.geom,
    st_buffer(event_point.geom, 100) AS "Buffer",

FROM public.event_point

SELECT 
    building.id
    building.address
FROM 
    building, "Buffer"
WHERE
    ST_within(building.geom, "Buffer".geom)
  • 4
    The question isn't totally clear. However, in general, it is better to use ST_DWithin than ST_Buffer -- it amounts to the same thing. Saying ST_DWithin(geom1, geom2, 1000) is the same as saying ST_Intersecs(geom1, ST_Buffer(geom2,1000)) except that the first is much more efficient. – John Powell Feb 24 '15 at 15:36
  • You are completely right! I ended up using you suggested ST_DWithin. It worked much faster compared to use the combined query. 40 seconds faster! – geogrow Feb 25 '15 at 10:06
  • Glad it helped. – John Powell Feb 25 '15 at 10:39
3

Put your first query in the from clause of the 2nd: something like that should work:

SELECT building.id building.address FROM building, (SELECT event_point.id, event_point.geom, st_buffer(event_point.geom, 100) AS buffergeom FROM public.event_point) buffer WHERE ST_within(building.geom, buffer.buffergeom)

  • This only works if there is only one row in the event_point table; otherwise you'll need a WHERE clause to limit to one row, or a JOIN to merge multiple rows correctly. – Vince Feb 24 '15 at 16:05
  • This worked, thanks for explaining it how to build a query like that! However, I ended up using John Barca suggestion because the query was much faster to return – geogrow Feb 25 '15 at 10:07

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