postgis之Polygon/MultiPolygon in a single column；面和多面存储在一个字段

postgresql空间字段存储多种不同类型polygon、multipolygon等情况

创建表时

CREATE table my_table(
  gid serial primary key,
  geom geometry(Polygon,4326)
);

修改已有表

ALTER TABLE my_table ALTER COLUMN geom TYPE geometry(Geometry,4326);

INSERT INTO my_table(geom)
VALUES
  ('SRID=4326;POLYGON EMPTY'),
  ('SRID=4326;MULTIPOLYGON EMPTY');