create table tree (id int, id2 int null)
go
insert tree values ( 1 , null)
insert tree values ( 2 , null)
insert tree values ( 3 ,  2 )
insert tree values ( 7 ,  1 )
insert tree values ( 4 ,  3 )
insert tree values ( 5 , null)
insert tree values ( 6 ,  2 )
go
select id, id as id2 from tree where coalesce(id2, - 1  ) = - 1 
union
select * from tree where coalesce(id2, - 1  ) >  0 
order by  2 , 1 
go

ID   ID2   MSG
 1     null   Topic # 1 
 2     null   Topic # 2 
 3      2       Topic # 2 
 4      3       Topic # 2 
 5     null   Topic # 5 
 6      2       Topic # 2 
 7      1       Topic # 1 

alter table Tree add msg char( 20 )
go
update tree set 
    msg=case when coalesce(id2, - 1 )= -  1  then 'Topic #' + cast(id as char( 2 ))
        else 'Topic #' + cast(id2 as char( 2 ))
        end
go
select id, id as id2, msg from tree where coalesce(id2, - 1  ) = - 1 
union
select * from tree where coalesce(id2, - 1  ) >  0 
order by  2 , 1 
go

create procedure usp_GetTreeMsg
    as
begin
     /* выборка id */ 
     /* 
    тут нужно проверить существование временной таблы 
    и удалить, если она есть. Как - не помню сейчас.   
    Посмотри на форуме. 
    */ 
    select id, id as id2 into #temp1 from tree where coalesce(id2, - 1  ) = - 1 
    union
    select * from tree where coalesce(id2, - 1  ) >  0 
    order by  2 , 1 

     /* "подключение" текста;
        условие - уникальность id */ 
    select t1.id, t1.id2, t2.msg 
        from #temp1 t1, tree t2
        where t2.id = t1.id

     /* удалим времянку */ 
    drop table #temp1
end