21 lines
573 B
MySQL
21 lines
573 B
MySQL
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-- Function by Stuart Lynn for a simple interpolation of a value
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-- from a polygon table over an arbitrary polygon
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-- (weighted by the area proportion overlapped)
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CREATE OR REPLACE
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FUNCTION cdb_overlap_sum(geom geometry, target_table_name text, target_column text)
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RETURNS numeric AS
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$$
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DECLARE
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result numeric;
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BEGIN
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EXECUTE Format('
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SELECT sum(%I*ST_Area(St_Intersection($1, a.the_geom))/ST_Area(a.the_geom))
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FROM %I AS a
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WHERE $1 && a.the_geom
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', target_column, target_table_name)
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USING geom
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INTO result;
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RETURN result;
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END;
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$$ LANGUAGE plpgsql;
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