mssqlserver分区表的左值与右值

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.

Partition1234
Valuescol1 <= 1col1 > 1 AND col1 <= 100col1 > 100 AND col1 <=1000col1 > 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.

Partition1234
Valuescol1 < 1col1 >= 1 AND col1 < 100col1 >= 100 AND col1 < 1000col1 >= 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.

Partition12...1112
Valuesdatecol < February 1, 2003datecol >= February 1, 2003 AND datecol < March 1, 2003 datecol >= November 1, 2003 AND col1 < December 1, 2003datecol >= December 1, 2003
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