how do I use the id sequence of “B” table in my “A” table?

Question

The issue is the following:

I have a table (let's name it table A ) and another table (table B ). What I need is to share the sequence of the table B and use it in A , so that I have 2 different tables, but every time I insert a row into one of the tables, it would behave like the 2 tables were one table, like this:

table A:          table B:

 id|               id|
  4|                1|
  5|                2|
  6|                3|  
  8|                7|  

I could not find out how to do this, so instead I created an on-update trigger which updates the id of the row I inserted in the table A and replaces with the next value of the sequence of the table B , the code is the following:

CREATE OR REPLACE FUNCTION credo.atz_id_reserva()
  RETURNS trigger AS
$BODY$
    BEGIN
        IF (TG_OP = 'INSERT') THEN

            UPDATE credo.reserva_pto_cta
            SET id = (select nextval('credo.documento_id_seq'));

        END IF;
        RETURN NULL;
    END;
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;
ALTER FUNCTION credo.atz_id_reserva()
  OWNER TO postgres;

Did I do something wrong, is anything missing?

Answer 1

But that is so simple:

CREATE SEQUENCE shared_seq;

CREATE TABLE a (
   id bigint PRIMARY KEY DEFAULT nextval('shared_seq'),
   ...
);

CREATE TABLE b (
   id bigint PRIMARY KEY DEFAULT nextval('shared_seq'),
   ...
);