数据库中分组第N条记录获取方式

数据库中分组第N条记录获取方式

 

第一条记录Oracle：

select * from(select row_number() over(partition by num order by num) gid,* from tb) tmp where gid=1；

  ROW_NUMBER()

 

 

说明：返回结果集分区内行的序列号，每个分区的第一行从 1 开始。

语法：ROW_NUMBER () OVER ( [ <partition_by_clause> ] <order_by_clause> ) 。

备注：ORDER BY 子句可确定在特定分区中为行分配唯一 ROW_NUMBER 的顺序。

参数：<partition_by_clause> ：将 FROM 子句生成的结果集划入应用了 ROW_NUMBER 函数的分区。 

      <order_by_clause>：确定将 ROW_NUMBER 值分配给分区中的行的顺序。

返回类型：bigint 。

 

示例：

/*以下示例将根据年初至今的销售额，返回 AdventureWorks 中销售人员的 ROW_NUMBER。*/

USE AdventureWorks
GO
SELECT c.FirstName, c.LastName, ROW_NUMBER() OVER(ORDER BY SalesYTD DESC) AS 'Row Number', s.SalesYTD, a.PostalCode
FROM Sales.SalesPerson s JOIN Person.Contact c on s.SalesPersonID = c.ContactID
JOIN Person.Address a ON a.AddressID = c.ContactID
WHERE TerritoryID IS NOT NULL AND SalesYTD <> 0
/*
FirstName  LastName    Row Number  SalesYTD      PostalCode
---------  ----------  ----------  ------------  ----------------------------
Shelley    Dyck        1           5200475.2313  98027
Gail       Erickson    2           5015682.3752  98055
Maciej     Dusza       3           4557045.0459  98027
Linda      Ecoffey     4           3857163.6332  98027
Mark       Erickson    5           3827950.238   98055
Terry      Eminhizer   6           3587378.4257  98055
Michael    Emanuel     7           3189356.2465  98055
Jauna      Elson       8           3018725.4858  98055
Carol      Elliott     9           2811012.7151  98027
Janeth     Esteves     10          2241204.0424  98055

Martha     Espinoza    11          1931620.1835  98055
Carla      Eldridge    12          1764938.9859  98027
Twanna     Evans       13          1758385.926   98055
(13 行受影响)
*/

/*以下示例将返回行号为 50 到 60（含）的行，并以 OrderDate 排序。*/ 
USE AdventureWorks;
GO
WITH OrderedOrders AS
(SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (order by OrderDate)as RowNumber
FROM Sales.SalesOrderHeader ) 
SELECT * 
FROM OrderedOrders 
WHERE RowNumber between 50 and 60;
/*
SalesOrderID OrderDate               RowNumber
------------ ----------------------- --------------------
43708        2001-07-03 00:00:00.000 50
43709        2001-07-03 00:00:00.000 51
43710        2001-07-03 00:00:00.000 52
43711        2001-07-04 00:00:00.000 53
43712        2001-07-04 00:00:00.000 54
43713        2001-07-05 00:00:00.000 55
43714        2001-07-05 00:00:00.000 56
43715        2001-07-05 00:00:00.000 57
43716        2001-07-05 00:00:00.000 58
43717        2001-07-05 00:00:00.000 59
43718        2001-07-06 00:00:00.000 60
(11 行受影响)
*/