postgresql transpose with different attribute row - sql

Question

This is the first time i used transpose
so i dont know if what i want is possible or not
this is my query
SELECT *
FROM crosstab(
'select p.name, a.attributekey, a.attributevalue
from productz p
join attribute a on a.itemid=p.id
order by p.name, a.attributekey')
AS final_result(name varchar, interface varchar, negativemargin varchar,parity varchar);
select p.name, a.attributekey, a.attributevalue
from productz p
join attribute a on a.itemid=p.id
order by p.name, a.attributekey;
here's the link
http://rextester.com/IQNSY51011
but the output is different than what i want, because productz 1 have two row and the productz 2 have 3 row
name interface negativemargin parity
dufan true true NULL
waterboom android true false
the output i want is this below without insert interface,Null to database
name interface negativemargin parity
dufan NULL true true
waterboom android true false
Note: please click "run it" after opening the link

Answer 1

Solution to your problem:
SELECT *
FROM crosstab(
'select p.name, a.attributekey, a.attributevalue
from productz p
join attribute a on a.itemid=p.id
order by p.name, a.attributekey',
'SELECT DISTINCT attributekey FROM attribute ORDER BY 1')
AS final_result(name varchar, interface varchar, negativemargin varchar,parity varchar);
LINK: http://rextester.com/OPNK82802
Use crosstab(text, text) with 2 input parameters.
The second parameter can be any query that returns one row per attribute matching the order of the column definition at the end.
What is the problem with CROSSTAB(text) i.e. crosstab with 1 parameter?
The main limitation of the single-parameter form of crosstab is that it treats all values in a group alike, inserting each value into the first available column. If you want the value columns to correspond to specific categories of data, and some groups might not have data for some of the categories, that doesn't work well. The two-parameter form of crosstab handles this case by providing an explicit list of the categories corresponding to the output columns.
For more info on crosstab follow the below link:
https://www.postgresql.org/docs/9.2/static/tablefunc.html