I have many tables with geometry attribute which is saved in Postgis database. These tables are basically from more than one shapefiles which is stored in Postgis using geotools.

Now I want a common table to handle all the geom attributes in the table, as shown in the below example

For eg:

enter image description here

Is there a way to do this using PostGIS? Initially the Table geom_all with geom column contains NULL value. I tried updating the values using JOINS with the below query example.

 UPDATE Geom_all g SET geom = (SELECT geom FROM Table-1 t WHERE g.id = t.id);

But this overrides with every new value i update in the geom column and also the sub query should return only 1 row, which in my case is not. I am not sure whether I can achieve this task using JOINS, it would be helpful to know if there is any other way to solve this.

NOTE: All the geom column contains geometry_type as MULTIPOLYGON and ST_SRID as 4326.

  • 1
    Can you union all the rows together from tables 1, 2 etc. ? You migt want a new column to give all the rows a unique ID
    – Dave C
    Commented Nov 22, 2018 at 13:02
  • Yes Dave I tried doing a ST_union (geom), but this removes the ID info. How do i handle this? however I need the geom specific ID info to map other attributes based on the ID later.
    – GeoFresher
    Commented Nov 22, 2018 at 13:14
  • Answer below was what I was refering to. ST_Union is trying to 'join' the geometries, where you just want to union the rows.
    – Dave C
    Commented Nov 22, 2018 at 14:30

1 Answer 1


If I understand correctly, you want to merge the rows from multiple tables. You don't need to alter the geometry

Create table geom_all as
Select ID, geom from table1
select ID, geom from table2
select ID, geom from table 3;

or if the table already exists:

Insert into geom_all (select ID, geom from table1);
  • I didnt expect it to be so straight forward, thank you @JGH :)
    – GeoFresher
    Commented Nov 22, 2018 at 14:18

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