從postgis中的查詢插入表格

Question

我嘗試從查詢中插入表格geofield中的多邊形。該表geofield的定義是這樣的：

CREATE TABLE geofield(id SERIAL PRIMARY KEY, field GEOMETRY); 

insert into geofield(field) values (myfield) 
SELECT 
    'POLYGON(('||cast((select lat from coordinates where id=1)as varchar)||' '|| 
     cast((select lon from coordinates where id=1)as varchar)||','|| 
     cast((select lat from coordinates where id=2)as varchar)||' '|| 
     cast((select lon from coordinates where id=2)as varchar)||','|| 
     cast((select lat from coordinates where id=3)as varchar)||' '|| 
     cast((select lon from coordinates where id=3)as varchar)||','|| 
     cast((select lat from coordinates where id=4)as varchar)||' '|| 
     cast((select lon from coordinates where id=4)as varchar)||','|| 
     cast((select lat from coordinates where id=1)as varchar)||' '|| 
     cast((select lon from coordinates where id=1)as varchar)||'))') AS myfield; 

的SELECT獨自返回我：

POLYGON((46.744628268759314 6.569952920654968,46.74441692818192 6.570487107359068,46.74426116111054 6.570355867853787,46.74447250168793 6.569821681149689,46.744628268759314 6.569952920654968)) 

但它不工作，我ST_GeomFromText但同樣的結果也tryed。

Answer 1

我會避免與文字串聯工作，並與普通PostGIS functions工作，而不是：

SELECT 
    /* Make a polygon from the linestring */ 
    ST_MakePolygon(
     /* Close the polygon */ 
     ST_AddPoint(
      t.linestring, 
      ST_StartPoint(t.linestring) 
     ) 
    ) 
FROM (
    SELECT 
     /* Aggregate into a linestring */ 
     ST_MakeLine(ST_MakePoint(c.lon, c.lat) ORDER BY c.id) AS linestring 
    FROM coordinates AS c 
) t 
; 

按照你prior question，你可以把它從json直接返回，如果你想：

SELECT 
    /* Make a polygon from the linestring */ 
    ST_MakePolygon(
     /* Close the polygon */ 
     ST_AddPoint(
      t.linestring, 
      ST_StartPoint(t.linestring) 
     ) 
    ) 
FROM (
    SELECT 
     /* Aggregate into a linestring */ 
     ST_MakeLine(ST_MakePoint(c.lon, c.lat) ORDER BY c.id) AS linestring 
    FROM 
    (
     SELECT 
      e.id, 
      (e.element->>'lat')::numeric AS lat, 
      (e.element->>'lon')::numeric AS lon 
     FROM 
      field AS f, 
      json_array_elements(f.data->'vertices') WITH ORDINALITY AS e(element, id) 
    ) AS c 
) t 
; 

Answer 2

該字符串採用正確的WKT格式，所以這不是問題。問題是您的經度和緯度值反轉，並且INSERT的語法錯誤。你也應該將字符串轉換爲geometry第一：

INSERT INTO geofield(field) 
    SELECT ST_GeomFromText(
     'POLYGON(('||cast((select lat from coordinates where id=1)as varchar)||' '|| 
      cast((select lon from coordinates where id=1)as varchar)||','|| 
      cast((select lat from coordinates where id=2)as varchar)||' '|| 
      cast((select lon from coordinates where id=2)as varchar)||','|| 
      cast((select lat from coordinates where id=3)as varchar)||' '|| 
      cast((select lon from coordinates where id=3)as varchar)||','|| 
      cast((select lat from coordinates where id=4)as varchar)||' '|| 
      cast((select lon from coordinates where id=4)as varchar)||','|| 
      cast((select lat from coordinates where id=1)as varchar)||' '|| 
      cast((select lon from coordinates where id=1)as varchar)||'))'); 

但這一切很浪費的，不適合大的多邊形。只要你的多邊形組成的單環，你可以做到這一點，這將是更快，不易出錯：

INSERT INTO geofield(field) 
    SELECT ST_GeomFromText('POLYGON((' || coords.c || ',' || coord1.c || '))', 4326) 
    FROM 
     (SELECT string_agg(lon::text || ' ' || lat::text, ',' ORDER BY id) AS c 
      FROM coordinates) coords, 
     (SELECT lon::text || ' ' || lat::text AS c 
      FROM coordinates 
      WHERE id = 1) coord1; 

第一個子查詢字符串所有座標一起，而第二隻獲取第一個座標來關閉多邊形。與儘可能多的點共同工作。