http://blogs.msdn.com/b/psssql/archive/2010/09/28/case-of-using-filtered-statistics.aspx

数据偏重,一个区域有0行,其余的都来自不同的区域.
以下是重现问题的整个代码

create table Region(id int,name nvarchar(100)) 
go 
create table Sales(id int,detail int) 
go 
create clustered index d1 on Region(id) 
go 
create index ix_Region_name on Region(name) 
go 
create statistics ix_Region_id_name on Region(id,name) 
go 
create clustered index ix_Sales_id_detail on Sales(id,detail) 
go

-- only two values in this table as lookup or dim table 
insert Region values(0,'Dallas') 
insert Region values(1,'New York') 
go

set nocount on 
-- Sales is skewed 
insert Sales values(0,0) 
declare @i int 
set @i = 1 
while @i <= 1000 begin 
insert Sales  values (1,@i) 
set @i = @i + 1 
end 
go

update statistics Region with fullscan 
update statistics Sales with fullscan 
go

set statistics profile on 
go 
--note that this query will over estimate 
-- it estimate there will be 500.5 rows 
select detail from Region join Sales on Region.id = Sales.id where name='Dallas' option (recompile) 
--this query will under estimate 
-- this query will also estimate 500.5 rows in fact 1000 rows returned 
select detail from Region join Sales on Region.id = Sales.id where name='New York' option (recompile) 
go

set statistics profile off 
go

create statistics Region_stats_id on Region (id) 
where name = 'Dallas' 
go 
create statistics  Region_stats_id2 on Region (id) 
where name = 'New York' 
go

set statistics profile on 
go 
--now the estimate becomes accurate (1 row) because 
select detail from Region join Sales on Region.id = Sales.id where name='Dallas' option (recompile)

--the estimate becomes accurate (1000 rows) because stats Region_stats_id2 is used to evaluate 
select detail from Region join Sales on Region.id = Sales.id where name='New York' option (recompile) 
go

set statistics profile off

我的问题是我们有两个表上可用的统计信息

sp_helpstats 'region','all'
sp_helpstats 'sales','all'

表格区域：

statistics_name   statistics_keys
d1                    id
ix_Region_id_name     id,name
ix_Region_name        name

桌面销售：

statistics_name    statistics_keys
ix_Sales_id_detail     id,detail

为什么下面的查询出现错误

select detail from Region join Sales on Region.id = Sales.id where name='Dallas' option (recompile)

--the estimate becomes accurate (1000 rows) because stats Region_stats_id2 is used to evaluate 
select detail from Region join Sales on Region.id = Sales.id where name='New York' option (recompile)

2.当我根据作者创建过滤的统计信息时,我可以正确地看到估计,但为什么我们需要创建过滤的统计信息,我怎么说我需要筛选统计信息,因为即使我创建简单的统计信息,我得到相同的结果.

最好我遇到了这么远
奇怪的tripp倾斜统计视频
技术统计白皮书

但是仍然无法理解为什么筛选的统计数据在这里有所不同

提前致谢.
更新：7/4

马丁和詹姆斯之后回答问题：

有什么办法可以避免数据偏移
除了kimberely脚本之外,还有一种方法可以计算一个值的行数.

2.您有遇到任何与您的经验数据偏差有关的问题.我认为这取决于大桌子.但是我正在寻找一些详细的答案

3.我们必须花费sql的成本来扫描表格,以及一些阻塞,有时候会在触发更新stats的时候出现一个查询.在维护统计信息时,您会看到除此之外的开销.

原因是我正在考虑根据基于DTA输入的几个条件创建文件统计.

再次感谢