原文:SQL Server表分區的NULL值問題

SQL Server表分區的NULL值問題

SQL Server表分區只支持range分區這一種類型，往往會被大家吐槽

人家MySQL支持四種類型：RANGE分區、LIST分區、HASH分區、KEY分區

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共同點是MySQL跟SQL Server也有分區對齊的問題，都是水平切分，大家都允許分區列存在NULL值

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這次我們測試SQL Server表分區的分區列的NULL值，究竟NULL值是被存放在哪個區間，以前一直沒有注意

測試腳本

--1.創建文件組 ALTER DATABASE [sss] ADD FILEGROUP [FG_TinyBlog_Id_01]ALTER DATABASE [sss] ADD FILEGROUP [FG_TinyBlog_Id_02]ALTER DATABASE [sss] ADD FILEGROUP [FG_TinyBlog_Id_03]ALTER DATABASE [sss] ADD FILEGROUP [FG_TinyBlog_Id_04]ALTER DATABASE [sss] ADD FILEGROUP [FG_TinyBlog_Id_05]--2.創建文件 ALTER DATABASE [sss] ADD FILE (NAME = N'FG_TinyBlog_Id_01_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_01_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB ) TO FILEGROUP [FG_TinyBlog_Id_01];ALTER DATABASE [sss] ADD FILE (NAME = N'FG_TinyBlog_Id_02_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_02_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB ) TO FILEGROUP [FG_TinyBlog_Id_02];ALTER DATABASE [sss] ADD FILE (NAME = N'FG_TinyBlog_Id_03_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_03_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB ) TO FILEGROUP [FG_TinyBlog_Id_03];ALTER DATABASE [sss] ADD FILE (NAME = N'FG_TinyBlog_Id_04_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_04_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB ) TO FILEGROUP [FG_TinyBlog_Id_04];ALTER DATABASE [sss] ADD FILE (NAME = N'FG_TinyBlog_Id_05_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_05_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB ) TO FILEGROUP [FG_TinyBlog_Id_05];--3.創建分區函數 CREATE PARTITION FUNCTION Fun_TinyBlog_Id(INT) AS RANGE LEFT FOR VALUES(-10,0,1,6)--4.創建分區方案 CREATE PARTITION SCHEME [Sch_TinyBlog_Id] AS PARTITION [Fun_TinyBlog_Id] TO([FG_TinyBlog_Id_01],[FG_TinyBlog_Id_02],[FG_TinyBlog_Id_03],[FG_TinyBlog_Id_04],[FG_TinyBlog_Id_05]) View Code

插入測試數據

USE [sss]CREATE TABLE TinyBlog(id INT NULL,NAME VARCHAR(100)) ON [Sch_TinyBlog_Id](id)SELECT * FROM TinyBlog ORDER BY id INSERT INTO [dbo].[TinyBlog]( [id], [NAME] ) VALUES ( NULL, -- id - int'3232' -- NAME - varchar(100) )INSERT INTO [dbo].[TinyBlog]( [id], [NAME] ) VALUES ( -2, -- id - int'-2' -- NAME - varchar(100) )INSERT INTO [dbo].[TinyBlog]( [id], [NAME] ) VALUES ( 66, -- id - int'66' -- NAME - varchar(100) )INSERT INTO [dbo].[TinyBlog]( [id], [NAME] ) VALUES ( 0, -- id - int'0' -- NAME - varchar(100) )INSERT INTO [dbo].[TinyBlog]( [id], [NAME] ) VALUES ( -30, -- id - int'-30' -- NAME - varchar(100))

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表數據如下

SELECT * FROM TinyBlog ORDER BY id

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分區分布

--查看分區架構文件組分布 SELECT CONVERT(VARCHAR(MAX), ps.name) AS partition_scheme ,p.partition_number ,CONVERT(VARCHAR(MAX), ds2.name) AS filegroup ,CONVERT(VARCHAR(MAX), ISNULL(v.value, ''), 120) AS range_boundary ,STR(p.rows, 9) AS rows FROM sys.indexes iJOIN sys.partition_schemes ps ON i.data_space_id = ps.data_space_idJOIN sys.destination_data_spaces dds ON ps.data_space_id = dds.partition_scheme_idJOIN sys.data_spaces ds2 ON dds.data_space_id = ds2.data_space_idJOIN sys.partitions p ON dds.destination_id = p.partition_numberAND p.object_id = i.object_idAND p.index_id = i.index_idJOIN sys.partition_functions pf ON ps.function_id = pf.function_idLEFT JOIN sys.Partition_Range_values v ON pf.function_id = v.function_idAND v.boundary_id = p.partition_number- pf.boundary_value_on_right WHERE i.object_id = OBJECT_ID('TinyBlog')AND i.index_id IN ( 0, 1 ) ORDER BY p.partition_number--分區區間 --SELECT * FROM sys.partition_range_values View Code

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分區情況

--分區情況 SELECT c.* ,b.[groupname] AS '分區方案對應的文件組名稱' ,d.name '當前分區函數對應的分區方案' FROM sys.destination_data_spaces AS aINNER JOIN sysfilegroups AS b ON a.[data_space_id] = b.[groupid]INNER JOIN ( SELECT $PARTITION.Fun_TinyBlog_Id(id) AS 分區編號 ,MIN(id) AS Min_value ,MAX(id) AS Max_value ,COUNT(id) AS 記錄數FROM [dbo].[TinyBlog]GROUP BY $PARTITION.Fun_TinyBlog_Id(id)) AS c ON c.[分區編號] = a.[destination_id]INNER JOIN sys.partition_schemes AS d ON a.[partition_scheme_id] = d.data_space_id ORDER BY c.[分區編號] View Code

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第二個視圖直接把NULL值忽略了

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根據第一個視圖，我們畫出一個總結圖

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分析一下

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總結

結論其實很清晰，分區列不要允許NULL，如果允許列，那么我們交換分區歸檔數據的時候就會有麻煩了，因為無法判斷分區列是NULL值的那些數據行是老數據還是新數據

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相關文章：

http://www.cnblogs.com/gaizai/archive/2010/11/05/1870071.html

https://msdn.microsoft.com/zh-cn/library/ms187802.aspx

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如有不對的地方，歡迎大家拍磚o(∩_∩)o?

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