SQL 计算累计和 sum() over( partition by order by )
https://www.cnblogs.com/lgx5/p/13746747.html
1).数据
2). sum(LABST) over()
3). sum(LABST) over(order by MATNR)
4).sum(LABST) over(order by MATNR,ZWEEK)
5).sum(LABST) over(partition by MATNR order by MATNR)
6).sum(LABST) over(partition by MATNR order by MATNR,ZWEEK)