相当于 ArcMap 联合的 PostGIS [英] PostGIS equivalent of ArcMap Union

问题描述

PostGIS/PostgreSQL 中

那么结果将是 1 个具有 7 个特征的 shapefile.(PostGIS 等效项:具有 7 行几何图形的表)

我查看了 ST_Intersect、ST_Union 和 ST_Collect，但找不到正确的组合.非常感谢您的帮助.

解决方案

这是一个基于

What is the equivalent in PostGIS / PostgreSQL of the "Union" operation in ArcMap?

Say you have two shapefiles with two features each. (PostGIS equivalent: two tables with two rows with polygon geometries)

then the result would be 1 shapefile with 7 features. (PostGIS equivalent: Table with 7 rows with geometries)

I've looked at ST_Intersect, ST_Union and ST_Collect but can't find the right combination. Your help is much appreciated.

解决方案

Here is a working query based on this answer from gis.stackexchange:

Read it from a) to d):

-- d) Extract the path number and the geom from the geometry dump
SELECT
  (dump).path[1] id,
  (dump).geom
FROM
(
  -- c) Polygonize the unioned rings (returns a GEOMETRYCOLLECTION)
  --    Dump them to return individual geometries
  SELECT
    ST_Dump(ST_Polygonize(geom)) dump
  FROM
  (
    -- b) Union all rings in one big geometry
    SELECT
      ST_Union(geom) geom
    FROM
    (
      -- a) First get the exterior ring from all geoms
      SELECT
        ST_ExteriorRing(geom) geom
      FROM
        rectangles
    ) a
  ) b
) c

Result:

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