--排名函数 ROW_NUMBER()  RANK(), DENSE_RANK(),NTILE()  Over()函数 为排名函数生成排序顺序、 select ROW_NUMBER() over(order by OrderDate)   as Romber,SalesOrderID,OrderDate  from SalesLT.SalesOrderHeader    ---创建一个单一的排序  SELECT ROW_NUMBER() OVER(partition by year(OrderDate),Month(OrderDate) order by orderdate) as rownumber,  SalesOrderID,OrderDate,ShipMethod    FROM SalesLT.SalesOrderHeader   WHERE SalesOrderID>=280 ORDER BY OrderDate;    ---ROW_NUMBER()    SELECT rowNumber ,SalesOrderNumber SalesOrderID,OrderDate  from (  select ROW_NUMBER() over(order by orderdate,SalesOrderID)  as rowNumber,* from   SalesLT.SalesOrderHeader   where SalesOrderID>293  ) as Q  where   rowNumber between 21 and 40  order by rowNumber;    --Rank()  DENSE_RANK()  EG:例如 张三跟王五 都是第二名 那么他们的Rank的值应为2     select productID,COUNT(*) as 'Count'   from SalesLT.SalesOrderDetail    group by ProductID   order  by COUNT(*);     select Productid,salescount,RANK() over(order by salescount) as 'Ranks',  DENSE_RANK() OVER(ORDER BY salescount) AS 'Dense_rank' from (select ProductID,COUNT(*) as salescount  from SalesLT.SalesOrderDetail  group by ProductID) as Q  group by 'Ranks';   运行结果：对比

通过 对比：Rank的结果与 DeseRank的结果不一样。。