[pguser]

test=*# select * from zeroseven ;
 order_id |   label   | index |    value
----------+-----------+-------+--------------
       11 | vorname   |     0 | max
       11 | nachname  |     1 | mustermann
       11 | anschrift |     2 | hauptstraße2
       11 | plz       |     3 | 12345
       11 | ort       |     4 | berlin
       12 | vorname   |     0 | andreas
       12 | nachname  |     1 | egal
       12 | anschrift |     2 | irgendwo
       12 | plz       |     3 | 4711
       12 | ort       |     4 | erde
(10 rows)

Time: 0,219 ms
test=*# select order_id, array_to_string(array_agg(vorname),'') as vorname, array_to_string(array_agg(nachname),'') as nachname, array_to_string(array_agg(anschrift),'') as anschrift, array_to_string(array_agg(plz),'') as plz, array_to_string(array_agg(ort),'') as ort from (select order_id, case when index=0 then value else null end as vorname, case when index=1 then value else null end as nachname, case when index=2 then value else null end as anschrift, case when index=3 then value else null end as plz, case when index=4 then value else null end as ort from zeroseven ) foo group by order_id;
 order_id | vorname |  nachname  |  anschrift   |  plz  |  ort
----------+---------+------------+--------------+-------+--------
       11 | max     | mustermann | hauptstraße2 | 12345 | berlin
       12 | andreas | egal       | irgendwo     | 4711  | erde
(2 rows)

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