code: public DatabaseRelationDefinition createDatabaseRelation(RelationID id) {
          if (!isStillMutable) {
              throw new IllegalStateException("Too late, cannot create a DB relation");
          }
          DatabaseRelationDefinition table = new DatabaseRelationDefinition(id, typeMapper);
          add(table, tables);
          add(table, relations);
          listOfTables.add(table);
          return table;
      }
docs: creates a database table (which can also be a database view)
  if the <name>id</name> contains schema than the relation is added
  to the lookup table (see getDatabaseRelation and getRelation) with
  both the fully qualified id and the table name only id
  
  @param id
  @return