Joining tables from different databases

The following example illustrates how to join two tables from different databases:

execute ibeblock (iii integer, ivc varchar(100))
returns (id integer, ename varchar(100), company varchar(100))
as
begin
 
-- drop database 'localhost/3060:c:\db1.fdb' user 'SYSDBA' password 'masterkey' clientlib 'C:\Program Files\Firebird\bin\fbclient.dll';
 
-- drop database 'localhost/3060:c:\db2.fdb' user 'SYSDBA' password 'masterkey' clientlib 'C:\Program Files\Firebird\bin\fbclient.dll';
 
  create database 'localhost/3060:c:\db1.fdb' user 'SYSDBA' password 'masterkey'
  page_size 4096 sql_dialect 3
  clientlib 'C:\Program Files\Firebird\bin\fbclient.dll'; 
 
  create database 'localhost/3060:c:\db2.fdb' user 'SYSDBA' password 'masterkey'
  page_size 4096 sql_dialect 3
  clientlib 'C:\Program Files\Firebird\bin\fbclient.dll';
 
  create connection db1 dbname 'localhost/3060:c:\db1.fdb'
  password 'masterkey' user 'SYSDBA'
  clientlib 'C:\Program Files\Firebird\bin\fbclient.dll';
 
  create connection db2 dbname 'localhost/3060:c:\db2.fdb'
  password 'masterkey' user 'SYSDBA'
  sql_dialect 3
  clientlib 'C:\Program Files\Firebird\bin\fbclient.dll';
 
  use db1;
 
  vstmt = 'create table "employees" ( ' || '
     id integer not null primary key,
     full_name varchar(100),
     company_id integer)';

  execute statement :vstmt; 
 
  commit;

  use default;

  select count(*) from help_items into :icount; 

  use db1;
 
  insert into "employees" (id, full_name, company_id) values (1, 'Alexander Khvastunov', 2);
  insert into "employees" (id, full_name, company_id) values (2, 'Bill Gates', 1);
  insert into "employees" (id, full_name, company_id) values (3, 'John Doe', NULL);
  insert into "employees" (id, full_name, company_id) values (4, 'Vladimir Putin', 3);
  insert into "employees" (id, full_name, company_id) values (5, 'Somebody', 15);

  use db2;
  
  execute statement
  'create table companies (
     id integer not null primary key,
     company_name varchar(100))';

  commit;

  insert into companies (id, company_name) values (1, 'Microsoft');
  insert into companies (id, company_name) values (2, 'HK-Software');
  insert into companies (id, company_name) values (3, 'The Kremlin?');

  commit;

  use db1;

  for execute statement 'select id, full_name, company_id from "employees"'
  into :id, :ename, :cid
  do
  begin
    use db2; 
 
    company = NULL; 

    select company_name from companies
    where id = :cid
    into :company;

    suspend;
  end

  close connection db1;
  close connection db2;
end