what is Partition Table?
Looking to optimize the performance of your SQL Server database? If your database contains very large tables, you may benefit from partitioning those tables onto separate filegroups. Allows you to spread data onto different physical disks, leveraging the concurrent performance of those disks to optimize query performance.
Partitioning a SQL Server database table is a three-step process:
1. Create the partition function
CREATE PARTITION FUNCTION customer_partfunc (int)
AS RANGE RIGHT
FOR VALUES (250000, 500000, 750000)
2. Create the partition scheme
CREATE PARTITION SCHEME customer_partscheme
AS PARTITION customer_partfunc
TO (fg1, fg2, fg3, fg4)
3. Partition the table
CREATE TABLE customers (FirstName nvarchar(40), LastName nvarchar(40), CustomerNumber int)
ON customer_partscheme (CustomerNumber)
Creates a scheme in the current database that maps the partitions of a partitioned table or index to filegroups. The number and domain of the partitions of a partitioned table or index are determined in a partition function. A partition function must first be created in a CREATE PARTITION FUNCTION statement before creating a partition scheme.
CREATE PARTITION SCHEME partition_scheme_name
AS PARTITION partition_function_name
[ ALL ] TO ( { file_group_name | [ PRIMARY ] } [ ,...n ] )
[ ; ]
The following example creates a partition function to partition a table or index into four partitions. A partition scheme is then created that specifies the filegroups to hold each one of the four partitions. This example assumes the filegroups already exist in the database.
CREATE PARTITION FUNCTION myRangePF1 (int)
AS RANGE LEFT FOR VALUES (1, 100, 1000);
GO
CREATE PARTITION SCHEME myRangePS1
AS PARTITION myRangePF1
TO (test1fg, test2fg, test3fg, test4fg);
The partitions of a table that uses partition function myRangePF1 on partitioning column col1 would be assigned as shown in the following table.
|
Filegroup |
test1fg |
test2fg |
test3fg |
test4fg |
|
Partition |
1 |
2 |
3 |
4 |
|
Values |
col1 <= 1 |
col1 > 1 AND col1 <= 100 |
col1 > 100 AND col1 <= 1000 |
col1 > 1000 |
