PostgreSQL

CREATE SEQUENCE my_test_table_primary_key_sequence INCREMENT BY 1 MINVALUE 1 NO MAXVALUE START WITH 1;
ALTER TABLE my_test_table ADD COLUMN id int4;
ALTER TABLE public.my_test_table ALTER COLUMN id SET DEFAULT nextval('my_test_table_primary_key_sequence');

 SELECT public.my_test_table.*,public.user.* FROM public.my_test_table INNER JOIN public.user ON public.my_test_table.user_id = public.user.id;