CREATE TABLE pointtable ( 
  id SERIAL PRIMARY KEY,
  name VARCHAR(128),
   geom GEOMETRY(Point, 3857)
);

CREATE INDEX pointtable_gix ON pointtable USING GIST (geom); 

INSERT INTO pointtable (name, geom) VALUES (‘p1‘,
  st_transform(ST_GeomFromText(‘POINT(105.1 30)‘, 4326)，3857）
);
INSERT INTO pointtable (name,geom) VALUES (‘p2‘,
  st_transform(ST_GeomFromText(‘POINT(105.1 30)‘, 4326)，3857）
);

INSERT INTO pointtable (name,geom) VALUES (‘p3‘,
 st_transform(ST_GeomFromText(‘POINT(105.1 30)‘, 4326)，3857）
);