我有一个包含4列的表：
Date Article Customer Turnover
我希望每6个月为每篇文章计算每个客户的营业额AVG。
From January to June ==> Turnover 1 of customer 1 for article 1
From Febrary to July ==> Turnover 2 customer 1 for article 1
From March to August ==> Turnover 3 customer 1 for article 1
From April to September ==> Turnover 4 customer 1 for article 1
From May to Obtober ==> Turnover 5 customer 1 for article 1
From June to November ==> Turnover 6 customer 1 for article 1
From July to December ==> Turnover 7 customer 1 for article 1
然后我按照每个6个月的所有营业额的sum进行划分，如上面的例子所示，但是对所有客户和所有文章都是。
我的数据如下：
Date Article IdCustomer Turnover
"2016-01-04" "ATSU" 17182 7146
"2016-01-05" "ATSU" 17182 3079
"2016-02-06" "ATSU" 17182 4012
"2016-02-22" "MFC" 17182 1398
"2016-03-04" "ATSU" 17182 4504
"2016-04-02" "ATSU" 17182 5214878
"2016-05-25" "ATSU" 17182 2365147
"2016-06-10" "ATSU" 17182 2598741
"2016-07-18" "ATSU" 17182 1845425
"2016-08-04" "ATSU" 17182 845350
"2016-09-12" "ATSU" 17182 87418
"2016-10-26" "ATSU" 17182 4012
"2016-11-25" "MFC" 17182 1398
"2016-12-21" "ATSU" 17182 4504
我有几个客户的相同例子。
问题是我无法找到一个解决方案来汇总每个cusomer每article个月的营业额。
有人请帮助我并给我一个解决方案如何解决这个问题？
谢谢;