How to transpose this table in postgresql - database

Question

I have this table:
lnumber | lname | bez_gem
---------+----------------+------------------------------
1 | name1 | Berg b.Neumarkt i.d.OPf.
1 | name1 | Altdorf b.Nürnberg
2 | name2 | Berg b.Neumarkt i.d.OPf.
2 | name2 | Altdorf b.Nürnberg
3 | name3 | Mainleus
3 | name3 | Weismain
4 | name4 | Weismain
4 | name4 | Mainleus
The code for the query is:
WITH double AS (
SELECT
partnumber,
bez_gem
FROM accumulation a, municipality b
WHERE ST_Intersects(a.geom, b.geom)
AND EXISTS (
SELECT
lnumber
FROM mun_more_than_once c
WHERE a.partnumber=c.lnumber)
ORDER BY partnumber)
SELECT
landslide.lnumber,
lname,
bez_gem
FROM double, landslide
WHERE double.partnumber=landslide.lnumber
ORDER BY lnumber
I want to transpose in this format
lnumber | lname | bez_gem1 | bez_gem2
---------+----------------+------------------------------------------------
1 | name1 | Berg b.Neumarkt i.d.OPf. | Altdorf b.Nürnberg
2 | name2 | Berg b.Neumarkt i.d.OPf. | Altdorf b.Nürnberg

Answer 1

It depends. If you always have two bez_gem per lnumber, you can simply use:
SELECT lnumber, lname
, min(bez_gem) AS bez_gem1
, max(bez_gem) AS bez_gem2
FROM test
GROUP BY 1,2
ORDER BY 1;
SQL Fiddle.
Note that the order of peers is undefined in your question. Collation rules (alphabetical order) decide in my example.
For an actual cross tabulation you would use the crosstab() function from the additional module tablefunc. But your table is missing a category name (no indication which row holds bez_gem1 and which bez_gem2). Explanation, details and links:
PostgreSQL Crosstab Query

Answer 2

SQLFiddle
Data
-- drop table if exists test;
create table test (lnumber int, lname varchar, bez_gem varchar);
insert into test values
(1 , 'name1' , 'Berg b.Neumarkt i.d.OPf.'),
(1 , 'name1' , 'Altdorf b.Nürnberg'),
(2 , 'name2' , 'Berg b.Neumarkt i.d.OPf.'),
(2 , 'name2' , 'Altdorf b.Nürnberg'),
(3 , 'name3' , 'Mainleus'),
(3 , 'name3' , 'Weismain'),
(4 , 'name4' , 'Weismain'),
(4 , 'name4' , 'Mainleus'),
(4 , 'name4' , 'XXMainleus')
;
Query
select
lnumber,
lname,
max(case when rn = 1 then bez_gem end) as bez_gem1,
max(case when rn = 2 then bez_gem end) as bez_gem2,
max(case when rn = 3 then bez_gem end) as bez_gem3
from
(
select
*,
row_number() over(partition by lname) rn
from
test
) a
group by
lnumber,
lname
Result
1;name1;Berg b.Neumarkt i.d.OPf.;Altdorf b.Nürnberg;
2;name2;Berg b.Neumarkt i.d.OPf.;Altdorf b.Nürnberg;
3;name3;Mainleus;Weismain;
4;name4;Weismain;Mainleus;XXMainleus
Old Answer
If you have only two possible rows for every lnumber (you should add this important info to your question), you can simply use min and max:
WITH double AS (
SELECT
partnumber,
bez_gem
FROM accumulation a, municipality b
WHERE ST_Intersects(a.geom, b.geom)
AND EXISTS (
SELECT
lnumber
FROM mun_more_than_once c
WHERE a.partnumber=c.lnumber)
ORDER BY partnumber)
SELECT
landslide.lnumber,
lname,
min(bez_gem) as bez_gem1,
max(bez_gem) as bez_gem2
FROM double, landslide
WHERE double.partnumber=landslide.lnumber
group by
landslide.lnumber,
lname
ORDER BY lnumber
If you have possibly more than two rows for every lnumber and you really need crosstab, there is a lot of questions regarding crosstab in PostgreSQL on SO (example). As an alternative you can try the following approach.
Because this is one-time analysis, you can easily get maximum number of unique bez_gem values:
select
landslide.lnumber,
count(distinct bez_gem) cnt
from
<<some_data>>
group by
landslide.lnumber
order by
cnt desc limit 1
Then you can use:
select
landslide.lnumber,
lname,
max(case when rn=1 then bez_gem end) as bez_gem1,
max(case when rn=2 then bez_gem end) as bez_gem2,
max(case when rn=3 then bez_gem end) as bez_gem3,
max(case when rn=4 then bez_gem end) as bez_gem4,
max(case when rn=5 then bez_gem end) as bez_gem5,
... up to cnt ...
from(
select
landslide.lnumber,
lname,
bez_gem,
row_number() over(partition by landslide.lnumber) rn
from
<<some_data>>
) a
group by
landslide.lnumber,
lname
For your data and 5 possible values it would look like:
WITH double AS (
SELECT
partnumber, bez_gem
FROM
accumulation a, municipality b
WHERE
ST_Intersects(a.geom, b.geom)
AND EXISTS (
SELECT lnumber
FROM mun_more_than_once c
WHERE a.partnumber=c.lnumber)
ORDER BY
partnumber
)
select
landslide.lnumber,
lname,
max(case when rn=1 then bez_gem end) as bez_gem1,
max(case when rn=2 then bez_gem end) as bez_gem2,
max(case when rn=3 then bez_gem end) as bez_gem3,
max(case when rn=4 then bez_gem end) as bez_gem4,
max(case when rn=5 then bez_gem end) as bez_gem5
from (
select
landslide.lnumber,
lname,
bez_gem,
row_number() over(partition by landslide.lnumber) rn
from
double, landslide
where
double.partnumber=landslide.lnumber
) a
group by
landslide.lnumber,
lname