mssqlserver分区表的左值与右值

最新推荐文章于 2023-10-31 14:02:43 发布

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最新推荐文章于 2023-10-31 14:02:43 发布

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本文详细介绍了SQL中的分区函数创建方法及使用场景，并通过实例对比了RANGE LEFT与RANGE RIGHT两种不同类型的分区函数，帮助读者更好地理解如何为数据表设置有效的分区策略。

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参考官方文档：

https://docs.microsoft.com/zh-cn/sql/t-sql/statements/create-partition-function-transact-sql

默认是Left

LEFT：第一个值属于第一个表，对应<=

RIGTH: 第一个值属于第二个表，对应<

如果数据按年进行分区，则RIGHT选项且每年的1月1日是合适的。如：

CREATE PARTITION FUNCTION [myDateRangePF1] (datetime)  
AS RANGE RIGHT FOR VALUES ('20030101', '20040101');  
这个有三个区：[0，20030101), [20030101, 20040101), [20040101, 999909999)

Examples

A. Creating a RANGE LEFT partition function on an int column

The following partition function will partition a table or index into four partitions.

tsql

CREATE PARTITION FUNCTION myRangePF1 (int)  
AS RANGE LEFT FOR VALUES (1, 100, 1000);

The following table shows how a table that uses this partition function on partitioning column col1 would be partitioned.

Partition	1	2	3	4
Values	col1 <= `1`	col1 > `1` AND col1 <= `100`	col1 > `100` AND col1 <=`1000`	col1 > `1000`

B. Creating a RANGE RIGHT partition function on an int column

The following partition function uses the same values for boundary_value [ ,...n ] as the previous example, except it specifies RANGE RIGHT.

tsql

CREATE PARTITION FUNCTION myRangePF2 (int)  
AS RANGE RIGHT FOR VALUES (1, 100, 1000);

The following table shows how a table that uses this partition function on partitioning column col1 would be partitioned.

Partition	1	2	3	4
Values	col1 < `1`	col1 >= `1` AND col1 < `100`	col1 >= `100` AND col1 < `1000`	col1 >= `1000`

C. Creating a RANGE RIGHT partition function on a datetime column

The following partition function partitions a table or index into 12 partitions, one for each month of a year's worth of values in a datetime column.

tsql

CREATE PARTITION FUNCTION [myDateRangePF1] (datetime)  
AS RANGE RIGHT FOR VALUES ('20030201', '20030301', '20030401',  
               '20030501', '20030601', '20030701', '20030801',   
               '20030901', '20031001', '20031101', '20031201');

The following table shows how a table or index that uses this partition function on partitioning column datecol would be partitioned.

Partition	1	2	...	11	12
Values	datecol < `February 1, 2003`	datecol >= `February 1, 2003` AND datecol < `March 1, 2003`		datecol >= `November 1, 2003` AND col1 < `December 1, 2003`	datecol >= `December 1, 2003`