我有一张table：

任务：

使用CTE创建数据透视表。
统计几年中每个月发出的订单：2011年至2013年。最后表格应包括四个字段：invoice_month、year_2011、year_2012、year_2013。月份字段必须将月份存储为1到12之间的数字。如果任何月份都没有下订单，则该月份的数字仍应包括在表中。
我可以使用以下查询解决此任务：

WITH year11
AS (
    SELECT EXTRACT(MONTH FROM invoice.invoice_date::TIMESTAMP) AS invoice_month
        ,COUNT(*) AS orders
    FROM invoice
    WHERE EXTRACT(YEAR FROM invoice.invoice_date::TIMESTAMP) = 2011
    GROUP BY invoice_month
    )
    ,year12
AS (
    SELECT EXTRACT(MONTH FROM invoice.invoice_date::TIMESTAMP) AS invoice_month
        ,COUNT(*) AS orders
    FROM invoice
    WHERE EXTRACT(YEAR FROM invoice.invoice_date::TIMESTAMP) = 2012
    GROUP BY invoice_month
    )
    ,year13
AS (
    SELECT EXTRACT(MONTH FROM invoice.invoice_date::TIMESTAMP) AS invoice_month
        ,COUNT(*) AS orders
    FROM invoice
    WHERE EXTRACT(YEAR FROM invoice.invoice_date::TIMESTAMP) = 2013
    GROUP BY invoice_month
    )
SELECT year11.invoice_month
    ,year11.orders AS year_2011
    ,year12.orders AS year_2012
    ,year13.orders AS year_2013
FROM year11
INNER JOIN year12 ON year11.invoice_month = year12.invoice_month
INNER JOIN year13 ON year11.invoice_month = year13.invoice_month

但是这个请求看起来太大了（或者不是？）。
1.在我的查询中使用CTE可以改进什么（我应该改进吗？）
1.其他工具来解决这个任务又快又漂亮？