如何使用 postgis 查询获取分组几何的 bbox?

How to get bbox of grouped geometries using postgis queries?

我在我的 postgresql table 中有一个点 table。

CREATE TABLE my_points(
    gid serial PRIMARY KEY,
    created_on TIMESTAMP NOT NULL,
    geog geography(POINTZ,4326) 
);

所以我想获取按 created_on 分组的更新数据的边界框。今天更新的数据是不同的位置。

例如table数据是这样的:

 gid      created_on             geog
 ------------------------------------
 1        08/15/2021 10:38:11    (1,2)
 2        08/15/2021 10:38:11    (2,2)
 3        08/15/2021 10:38:11    (3,2)
 4        08/15/2021 11:12:04    (1,2)
 5        08/15/2021 11:12:04    (2,4)

在此 table 中,按日期分为两组。 08/15/2021 10:38:11 有 ID (1,2,3) 和 08/15/2021 11:12:04 有 ID (4,5

所以我需要 select 查询两个边界框以按 created_on 日期分组。

我需要一个 seelct 查询来查找蓝色方形几何图形。

我怎样才能select这个?

使用 ST_UnionGROUP BY 创建点簇,然后使用 ST_Envelope or ST_Extent 之一绘制边界框:

ST_Envelope

Returns 所提供几何体的最小边界框,作为几何体:

SELECT 
  ST_Envelope(
    ST_Union(geog::geometry)) 
FROM my_points
GROUP BY created_on;

ST_Extent

检索给定几何或几何组的 BBOX:

WITH j (created_on,geog) AS (
  SELECT 
    created_on, ST_Union(geog::geometry)
  FROM my_points
  GROUP BY created_on
)
SELECT ST_Extent(geog) FROM j
GROUP BY created_on;

演示:db<>fiddle

CREATE TABLE my_points(
    gid serial PRIMARY KEY,
    created_on TIMESTAMP NOT NULL,
    geog geography(POINT,4326)
);

INSERT INTO my_points VALUES
(1,'2021-08-15 10:38:11','SRID=4326;POINT(-4.481927586167595 54.32254424440715)'),
(2,'2021-08-15 10:38:11','SRID=4326;POINT(-4.44759531077697 54.28408149183809)'),
(3,'2021-08-15 10:38:11','SRID=4326;POINT(-4.563638401597283 54.29169676415854)'),
(4,'2021-08-15 11:12:04','SRID=4326;POINT(-4.52449960765197 54.23234056232733)'),
(5,'2021-08-15 11:12:04','SRID=4326;POINT(-4.478494358628533 54.1893743942604)');

结果:

WITH j (created_on,geog) AS (
  SELECT 
    created_on, ST_Union(geog::geometry)
  FROM my_points
  GROUP BY created_on
)
SELECT ST_Extent(geog) FROM j
GROUP BY created_on;
                                   st_extent                                   
-------------------------------------------------------------------------------
 BOX(-4.563638401597283 54.28408149183809,-4.44759531077697 54.32254424440715)
 BOX(-4.52449960765197 54.1893743942604,-4.478494358628533 54.23234056232733)