Question

我有这个查询来获取在另一个geom中相交的geom的数量：

SELECT  count(evidensapp_polystructures.brgy_locat) AS high,
        evidensapp_polystructures.brgy_locat AS barangay,
        evidensapp_polystructures.municipali AS municipality
FROM evidensapp_floodhazard
INNER JOIN evidensapp_polystructures
      ON st_intersects(evidensapp_floodhazard.geom, evidensapp_polystructures.geom) 
      AND evidensapp_floodhazard.hazard= 'High'
GROUP BY evidensapp_polystructures.brgy_locat, evidensapp_polystructures.municipali;

如您所见，其hazard等于High。我想获得与hazard值相交的geom数量：Medium和Low。但是，如果某个几何图形已经在High中相交，则在Medium查询中排除，Low同样排除那些在High和Medium中相交的几何图形。

我有这个想法，也许使用CASE或者我需要得到几何的id然后在查询中尝试NOT IN但不知道如何去做。可能是因为我是PostgreSQL或任何数据库工作的新手。

以下是上述查询的示例结果：

预期结果应如下：

表格详情：

CREATE TABLE evidensapp_floodhazard (
  id serial NOT NULL,
  hazard character varying(6) NOT NULL,
  date_field character varying(60),
  geom geometry(MultiPolygon,32651),
  CONSTRAINT evidensapp_floodhazard_pkey PRIMARY KEY (id)
);

CREATE INDEX evidensapp_floodhazard_geom_id
  ON evidensapp_floodhazard USING gist (geom);

ALTER TABLE evidensapp_floodhazard CLUSTER ON evidensapp_floodhazard_geom_id;

CREATE TABLE evidensapp_polystructures (
  id serial NOT NULL,
  bldg_name character varying(100) NOT NULL,
  bldg_type character varying(50) NOT NULL,
  brgy_locat character varying(50) NOT NULL,
  municipali character varying(50) NOT NULL,
  province character varying(50) NOT NULL,
  geom geometry(MultiPolygon,32651),
  CONSTRAINT evidensapp_polystructures_pkey PRIMARY KEY (id)
);

CREATE INDEX evidensapp_polystructures_geom_id
  ON evidensapp_polystructures USING gist (geom);

ALTER TABLE evidensapp_polystructures CLUSTER ON evidensapp_polystructures_geom_id;

Answer 1

由于你几乎无法处理字符串＆＃34; High＆＃34;，＆＃34; Medium＆＃34;和＆＃34;低＆＃34;就比较而言，您必须使用子查询。一些CTE的解决方案可能是最干净的：

WITH hi AS (
  SELECT ps.id, ps.brgy_locat, ps.municipali
  FROM evidensapp_polystructures ps
  JOIN evidensapp_floodhazard fh ON fh.hazard = 'High'
                                 AND ST_Intersects(fh.geom, ps.geom)
), med AS (
  SELECT ps.id, ps.brgy_locat, ps.municipali
  FROM evidensapp_polystructures ps
  JOIN evidensapp_floodhazard fh ON fh.hazard = 'Medium'
                                 AND ST_Intersects(fh.geom, ps.geom)
  EXCEPT SELECT * FROM hi
), low AS (
  SELECT ps.id, ps.brgy_locat, ps.municipali
  FROM evidensapp_polystructures ps
  JOIN evidensapp_floodhazard fh ON fh.hazard = 'Low'
                                 AND ST_Intersects(fh.geom, ps.geom)
  EXCEPT SELECT * FROM hi
  EXCEPT SELECT * FROM med
)
SELECT brgy_locat AS barangay, municipali AS municipality, high, medium, low
FROM (SELECT brgy_locat, municipali, count(*) AS high
      FROM hi
      GROUP BY 1, 2) cnt_hi
FULL JOIN (SELECT brgy_locat, municipali, count(*) AS medium
      FROM med
      GROUP BY 1, 2) cnt_med USING (brgy_locat, municipali)
FULL JOIN (SELECT brgy_locat, municipali, count(*) AS low
      FROM low
      GROUP BY 1, 2) cnt_low USING (brgy_locat, municipali);

在三个CTE中，您首先要确定属于＆＃34;高＆＃34;的行？危险类别，然后是＆＃34;媒体＆＃34;危险类别，但EXCEPT那些已经在＆＃34;高＆＃34;类别，那么＆＃34;低＆＃34;危险类别除了那些列为＆＃34;高＆＃34;或＆＃34;中等＆＃34;。在主要查询中，然后加入3个CTE，其中每个barangay和市政府的计数在每个CTE的子查询中计算。使用FULL JOIN，以便在高等级的城市中没有结构的城镇和城市。危险等级也出现在结果中。

PostgreSQL：如果下一个查询与前一个查询相交，则排除几何

1 个答案: