造轮子：分页写法参考

http://www.cnblogs.com/Leo_wl/p/3273597.html

随着SQL Server版本的升级，常用的方法有三种：TOP，ROW_NUMBER，OFFSET/FETCH NEXT。

一. TOP

[b](1) 利用order by正反排序[/b]

declare @page_no int
declare @page_size int

select *
from (select top @page_size *
from (select top @page_size*@page_no * from split_pages order by ID) a
order by ID desc) b
order by ID

做完最里层select后，再对派生表查询时，index就没有效果了，而且越往后面要top更多的数据，这种写法会更慢。

(2) 利用NOT IN或者NOT EXISTS

declare @page_no int
declare @page_size int

select top @page_size *
from split_pages
where ID NOT IN (select top @page_size*(@page_no-1) ID from split_pages order by ID)
order by ID

通常在写SQL语句时，用IN/EXISTS不一样，如果逻辑不变的话， EXISTS的效率高。

不过，利用NOT IN分页，和用NOT EXISTS效果基本一样，因为都需要扫完全部数据。

(3) 利用ID大于MAX(ID)

declare @page_no int
declare @page_size int

select top @page_size *
from split_pages
where ID > (select MAX(ID) from (select top @page_size*(@page_no-1) ID from split_pages order by ID) t)
order by ID

在使用TOP分页时，这种用法效率最高。

二. ROW_NUMBER
SQL Server 2005开始的新语法，和ORACLE，DB2中的row_number()类似。性能比用TOP有所提升。

在利用ROW_NUMBER分页时，总页数/行数的计算，可以有这几种写法。
(1) 单独的SQL语句去获得总行数

select COUNT(*) AS TotRows
from split_pages
GO
declare @page_no int
declare @page_size int

set @page_no = 2
set @page_size = 10

;with tmp
AS
(
select *,
ROW_NUMBER() OVER(order by ID) num
from split_pages
)
select ID, Name
from tmp
where num BETWEEN (@page_size*(@page_no-1)+1) AND @page_size*@page_no
order by num

(2) 在ROW_NUMBER的同时用COUNT计算总行数

declare @page_no int
declare @page_size int

set @page_no = 2
set @page_size = 10

;WITH tmp
AS
(
select *,
ROW_NUMBER() OVER(order by ID) num,
COUNT(*) OVER() total
from split_pages
)
select ID, Name
from tmp
where num BETWEEN (@page_size*(@page_no-1)+1) AND @page_size*@page_no
order by num

(3) 仅使用ROW_NUMBER计算总行数，IO最少

declare @page_no int
declare @page_size int

set @page_no = 2
set @page_size = 10

;with tmp
as
(
select *,
ROW_NUMBER() OVER(order by ID) num,
ROW_NUMBER() OVER(order by ID desc) num_desc
from split_pages
)
select ID, Name, num_desc + num -1 as total
from tmp
where num BETWEEN (@page_size*(@page_no-1)+1) AND @page_size*@page_no
order by num

三. OFFSET/FETCH NEXT
SQL Server 2012的新语法，类似MYSQL，POSTGRESQL中的LIIMIT/OFFSET，据称性能比ROW_NUMBER又有了提升。

declare @page_no int
declare @page_size int

set @page_no = 3
set @page_size = 10

SELECT *,COUNT(*) OVER() AS Total
FROM split_pages
ORDER BY ID
OFFSET (@page -1) * @size ROWS
FETCH NEXT @size ROWS ONLY;