窗口函数 ROW_NUMBER

ROW_NUMBER:在窗口函数的分区、排序列 会为每一数据行分配唯一的序列值

最近在工作中经常会碰到，计算当前订单时该会员的第多少单以及会员的累积消费金额等情况

1：计算会员当前订单是该会员第几单(根据订单创建时间计算)

1 SELECT  OrderCode ,
2         CustCode ,
3         OrderMoney ,
4         CreateTime ,
5         ROW_NUMBER() OVER ( ORDER BY CreateTime ) AS OrderSeq
6 FROM    dbo.Sales_Order
7 WHERE   CustCode = ‘6702791‘;

2：除了计算每笔订单时该会员的第几单，同时还会关注，截止当前订单，会员累计消费金额

1 SELECT  OrderCode ,
2         CustCode ,
3         OrderMoney ,
4         CreateTime ,
5         ROW_NUMBER() OVER ( ORDER BY CreateTime ) AS OrderSeq ,
6         SUM(OrderMoney) OVER ( ORDER BY CreateTime RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW ) AS CurTotalMoney
7 FROM    dbo.Sales_Order
8 WHERE   CustCode = ‘6702791‘;

窗口函数也会涉及到一些性能的相关问题，有关窗口函数的索引优化，后续会补充进来。