Eu tenho uma tabela chamada comoProduct:

create table product (
    ProductNumber varchar(10),
    ProductName varchar(10),
    SalesQuantity int,
    Salescountry varchar(10)
);  

Valores da amostra:

insert into product values
  ('P1', 'PenDrive', 50,  'US')
, ('P2', 'Mouse',    100, 'UK')
, ('P3', 'KeyBoard', 250, 'US')
, ('P1', 'PenDrive', 300, 'US')
, ('P2', 'Mouse',    450, 'UK')
, ('P5', 'Dvd',      50,  'UAE');   

Eu quero gerar oSalescountry's nomes dinamicamente e mostram a soma deSalesQuantity venda nesse país.

Resultado esperado:

ProductName US    UK    UAE
----------------------------
PenDrive    350   0     0
Mouse       0     550   0
KeyBoard    250   0     0
Dvd         0     0     50

Eu fiz isso usando o SQL Server 2008 R2:

DECLARE @cols AS NVARCHAR(MAX),
        @query  AS NVARCHAR(MAX);

SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(SalesCountry) 
            FROM Product
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT ProductName, ' + @cols + ' from 
            (
                select ProductName
                    , SalesQuantity as q
                    , Salescountry
                from Product
           ) x
            pivot 
            (
                 SUM(q)
                for Salescountry in (' + @cols + ')
            ) p '

PRINT(@query);
execute(@query);

Como conseguir isso no Postgres?