使用PostgreSQL 9.3进行动态数据透视查询

我有一个名为Product的表：

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

样本值：

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

我想动态生成Salescountry的名称,并显示该国家的SalesQuantity销售总额.

预期结果：

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

我使用sql Server 2008 R2做到了：

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,'')

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);

如何在Postgres实现这一目标？

解决方法

SELECT *
FROM   crosstab (
   'SELECT ProductNumber,ProductName,Salescountry,SalesQuantity
    FROM   product
    ORDER  BY 1',$$SELECT unnest('{US,UK,UAE1}'::varchar[])$$
  ) AS ct (
   "ProductNumber" varchar,"ProductName"   varchar,"US"   int,"UK"   int,"UAE1" int);

详细说明：

> PostgreSQL Crosstab Query
> Pivot on Multiple Columns using Tablefunc

对不同数量的不同Salescountry进行完全动态查询？

> Dynamic alternative to pivot with CASE and GROUP BY