t1                t2
id name       id  name
 -- ----       --  ----
1  Pirate     1   Rutabaga
2  Monkey     2   Pirate
3  Ninja      3   Darth Vader
4  Spaghetti  4   Ninja

create table obj_class (
    class_id int identity(1,1),
    class_name varchar(64) not null,
  constraint obj_class_pk primary key clustered (class_id),
  constraint obj_class_uq unique (class_name)
)

create table obj_prop (
    class_id int not null,
    prop_name varchar(64) not null,
  constraint obj_prop_fk_obj_class foreign key (class_id) references obj_class (class_id)
)

select a.class_id, a.class_name, b.prop_name
  from obj_class a
    inner join obj_prop b on b.class_id = a.class.id

select table1.field1
  from table1
  where table1.field1 not in (select table2.field2 from table2)
union
select table2.field1
  from table2
  where table2.field1 not in (select table1.field2 from table1)