SQL Server 2014

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create table pn(
  id      int identity(1,1) primary key,
  proj_id int not null,
  pn      varchar(10) not null,
  mtyp_id int not null);
insert into pn (proj_id, pn, mtyp_id)
values (1, 'Cc',1), (1, 'Bb',2), (1, 'Aa',3), (2, 'Dd',2), (3, 'Ee',1), (3, 'Ff',3);
6 rows affected

create table mscht(
  id_mtyp int identity(1,1) primary key,
  masch   varchar(10) not null);
insert into mscht (masch)
values ('WSG'), ('HSG'), ('GSF'), ('WIP');
4 rows affected

create table docmap(
  ID_DM int identity(1,1) primary key,
  DN_ID int not null,
  PN_ID int not null);
insert into docmap (DN_ID, PN_ID)
values (1, 1), (1,2), (2,3), (3,4), (4,5), (5,6);
6 rows affected

create view v as  -- damit die Übersicht nicht verloren geht
select dn_id,
       cast('PN ' + pn + '(' + masch + ') ' as nvarchar) as zeile
from   docmap d
       inner join pn p
               on d.pn_id = p.id
       inner join mscht m
               on p.mtyp_id = m.id_mtyp;
with x as (
  select dn_id,
         zeile,
         -- Zeilen nach dn_id partitioniert durchnumerieren
         row_number() over (partition by dn_id order by dn_id) as rnum,
         -- Anzahl der Zeilen ermittel und merken
         count(*) over (partition by dn_id) as cnt
  from   v),
     y as (  -- Rekursion über alle Zeilen
  select dn_id,
         cast(x.zeile as nvarchar) as ganzezeile,
         zeile,
         rnum,
         cnt
  from   x
  where  rnum = 1
  union  all
  select y.dn_id,
         cast(x.zeile + char(13) + char(10) + y.ganzezeile as nvarchar),
         x.zeile,
         x.rnum,
         x.cnt
  from   x inner join y on x.dn_id = y.dn_id and
                           x.rnum = y.rnum + 1)
select dn_id, ganzezeile
from   y
where  rnum = cnt
order  by 1;


dn_id
ganzezeile


1
PN Bb(HSG) 
PN Cc(WSG)

2
PN Aa(GSF)

3
PN Dd(HSG)

4
PN Ee(WSG)

5
PN Ff(GSF)
dn_id	ganzezeile
1	PN Bb(HSG) PN Cc(WSG)
2	PN Aa(GSF)
3	PN Dd(HSG)
4	PN Ee(WSG)
5	PN Ff(GSF)