SQL SERVER2012新分页方式

guguda2008 2012-03-19 07:42:50

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SQL SERVER2012在ORDER BY 子句中加入了新元素offset,允许用户在排序完成的结果集中自定义输出行范围，大大简化了分页SQL的书写方式和效率。以下是与以前的两种分页方式的简单对比

use master

go

set nocount on

go

set showplan_text on

go

--2012的OFFSET分页方式

select number 

from spt_values

where type='p'

order by number offset 10 rows fetch next 5 rows only;

go

--2005的ROW_NUMBER分页方式

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分页方式

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)



*/

从查询计划来看，2012的查询计划中，offset直接操作了top迭代器，分页计划十分简单，看起来也比后两种简单明了。
而在系统预估的查询开销中，OFFSET占9%，ROW_NUMBER占45%，TOP占47%（加起来101% -_-||）,OFFSET占了绝对的优势。

在2008的更新中，我最喜欢的是MERGE，2012中就是OFFSET了。

博文地址
http://blog.csdn.net/guguda2008/article/details/7370398

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