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。
原文：http://www.cnblogs.com/wawa0210/p/6057977.html
