SQL SERVER2012新分頁方式

SQL SERVER2012在ORDER BY 子句中加入了新元素offset,允許用戶在排序完成的結果集中自定義輸出行范圍，大大簡化了分頁SQL的書寫方式和效率。以下是與以前的兩種分頁方式的簡單對比

use master
go
set nocount on
go
set showplan_text on
go

--2012的OFFSET分頁方式
select number 
from spt_values
where type='p'
order by number offset 10 rows fetch next 5 rows only;
go

--2005的ROW_NUMBER分頁方式
select number from (
select number,row_number() over(order by number) as num from spt_values where type='p'
) t where num between 11 and 15
order by number asc
go

--2000的TOP分頁方式
select number from (
select top 5 number from (
select top 15 number from spt_values where type='p' order by number asc
) t
order by number desc
) t 
order by number asc
go
set showplan_text off
go
/*
StmtText
----------------------------------------------------------------------------------------------------------
select number 
from spt_values
where type='p'
order by number offset 10 rows fetch next 5 rows only;

StmtText
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  |--Top(OFFSET EXPRESSION:((10)),TOP EXPRESSION:((5)))
       |--Index Scan(OBJECT:([mssqlsystemresource].[sys].[spt_values].[ix2_spt_values_nu_nc]),  WHERE:(CONVERT(nchar(3),[mssqlsystemresource].[sys].[spt_values].[type],0)=N'p') ORDERED FORWARD)

StmtText
---------------------------------------------------------------------------------------------------------------------------------------------------------------------
select number from (
select number,row_number() over(order by number) as num from spt_values where type='p'
) t where num between 11 and 15
order by number asc

StmtText
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  |--Sort(ORDER BY:([mssqlsystemresource].[sys].[spt_values].[number] ASC))
       |--Filter(WHERE:([Expr1005]>=(11) AND [Expr1005]<=(15)))
            |--Top(TOP EXPRESSION:(CASE WHEN (15) IS NULL OR (15)<(0) THEN (0) ELSE (15) END))
                 |--Sequence Project(DEFINE:([Expr1005]=row_number))
                      |--Segment
                           |--Index Scan(OBJECT:([mssqlsystemresource].[sys].[spt_values].[ix2_spt_values_nu_nc]),  WHERE:(CONVERT(nchar(3),[mssqlsystemresource].[sys].[spt_values].[type],0)=N'p') ORDERED FORWARD)

StmtText
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
select number from (
select top 5 number from (
select top 15 number from spt_values where type='p' order by number asc
) t
order by number desc
) t 
order by number asc

StmtText
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  |--Sort(ORDER BY:([mssqlsystemresource].[sys].[spt_values].[number] ASC))
       |--Sort(TOP 5, ORDER BY:([mssqlsystemresource].[sys].[spt_values].[number] DESC))
            |--Top(TOP EXPRESSION:((15)))
                 |--Index Scan(OBJECT:([mssqlsystemresource].[sys].[spt_values].[ix2_spt_values_nu_nc]),  WHERE:(CONVERT(nchar(3),[mssqlsystemresource].[sys].[spt_values].[type],0)=N'p') ORDERED FORWARD)

*/

從查詢計划來看，2012的查詢計划中，offset直接操作了top迭代器，分頁計划十分簡單，看起來也比后兩種簡單明了。

而在系統預估的查詢開銷中，OFFSET占9%，ROW_NUMBER占45%，TOP占47%（加起來101% -_-||）,OFFSET占了絕對的優勢。

在2008的更新中，我最喜歡的是MERGE，2012中就是OFFSET了。