I have a single table of over 1000 polygons in postgreSQL (with PostGIS), and I have a field "evaluation_type" that only receives two values, either 'good'(green) or 'bad'(red), as you can see in the picture below.
And in the attribute table I'd have - 'good' - 'bad' - 'fair': For the intersections
I'd like the result layer (the one containing the intersection) in a "2D" layer, in other words, I want no overlap between the intersects. It's because, in the end, the thing I'm looking for is to count, for each small little polygon, how many 'good' and 'bad' polygons it represents, see below the hypothetical attribute table I want to have.
id| evaluation | count_good | count_bad
1 | good | 223 | 0 2 | fair | 108 | 288 3 | bad | 0 | 278 4 | fair | 193 | 132 5 | fair | 183 | 198 6 | ...
- If the small polygon only represents a intersection of 'good' polygons it will receive an value of 'good' and will have 0 in the field 'count_bad'
- If the small polygon only represents a intersection of 'bad' polygons it will receive an value of 'bad' and will have 0 in the field 'count_good'
- If the small polygon represents a intersection of 'bad' and 'good' polygons it will receive an value of 'fair' and will have 0 counts > 0 in both fields 'count_good' and 'count_bad'
As far as I remember in ArcGIS Union tool, it would break the intersections. I realized that ST_Union behaves a bit different. I used the following code and it returned a dissolved polygon.
CREATE TABLE out_table AS SELECT ST_Union(geom) as geom FROM areas_demo;
Do you have a hint, how could I get such result I described?