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Table Partitioning refers to the organization of table data into numerous smaller storage units known as data partitions built on the defined values in a column or group of columns.

It is the horizontally splitting of the data of a large, logically single table set up into smaller physical pieces. However, when queries are performed, these partitions are stored across more than one filegroup in a database but are treated as a single entity, i.e., a single table.

Why Utilize Table Partitioning?

By distributing a large table into smaller partitions, you can advance query performance, and trim down involved costs. Partitioning large tables has the following management advantages and performance benefits:

• Smaller subsets of data can be accessed or moved swifter and more efficiently while sustaining data integrity. The time-consuming data operations can be made quicker by splitting them into a series of smaller tasks.
• By grouping more profoundly accessed data together into one partition, query performance can be amazingly boosted. So, when frequently accessed data is located together, query execution turns more effective. This also successfully offsets any overheads caused by upper levels of indexing.
• Maintenance operations develop swifter, and the downtime of the table is significantly trimmed down as these operations involve only a part of the entire data at once. It is also possible to customize and tailor the optimization of diverse partitions according to the need of each and every unit.
• If partitions are created based on the data utilization, targeted operations like bulk updates or such deletions can be very resourcefully managed. This scenario involves the partition of data as an alternative to searching through the complete table. Similarly, more frequently used data sets can be stored on quicker media. In comparison, the less regularly utilized partitions can be managed on low-priced and unhurried storage media, thus utilizing the tier-up storage far more competently.
• In RAID systems, analytical data access operations can be executed far more proficiently by striping the data files of the partitions across numerous disks.
• Partition level locking can be of assistance to trim down lock conflicts as equated to locking on the whole table. This compact lock escalation makes for far more resourceful data access, particularly in an exact and real-time system.

Diverse RDBMS propose numerous approaches to a partition of data in a table. If built-in backing and support are not obtainable for your needs, then alternative methods like UNION ALL views can be applied. However, they do not deliver similar performance advantages and gains.

What do you need to know before working on table partitioning?

When you deal with partitioning a table in SQL Server, the place to initiate is knowing the logical division of your data sets prior to you essentially implement the same. Here is what you require to comprehend and formerly explore to build partitions in the data table. 

• Partitioning column:
  Partitioning column(s) is the explicit column or group of columns utilized for partitioning a table. In SQL Server, all data categories that are valid for index columns usages can be worked upon as a partitioning column, excluding timestamp. Even the image, ntext, text, XML, varchar (max), nvarchar (max), varbinary (max) data types, .Net Framework user-defined type or alias data type columns cannot be utilized.
• Partition function:
  The partition function states how the rows of the partitioned table map to multiple partitions according to the values in the chosen partition columns. The partition function lays down the number of partitions and the partition boundaries for the table. It takes the absolute value of the partition column as an input and provides an explicit partition value as an output.
• Partition scheme:
  The partitions of a partition function are plotted to a set of filegroup as per the Partition Scheme characterization. By placing every partition in a distinct filegroup, the upkeep and backup of partitions turn more resourceful.
• Aligned index:
  For indexed tables, the index can be created utilizing a similar partition scheme as the table so that if SQL Server requires to alter partitions, both the data table and index can have the identical partition structure. For attaining this, the partition function of the index and data table should be matching.

How to build a partitioned table?

Partitioning can turn large tables better manageable and more scalable. Here we have explained four significant steps to build a partitioned table:

Step 1: Make filegroup(s) and related files to encompass the partitions utilized in the partition scheme.

Step 2: Decide on the partitioning column(s) and state a partition function that maps the specified rows of a table into partitions depending on the actual values of the partitioning column(s).

Step 3: Define a precise partition scheme that maps the table partitions linked to the filegroups.

Step 4: Building or modifying the table to agree on the partition scheme as per the exact storage location.

Partitioning utilizing Transact-SQL

Let’s explore partitioning using Transact-SQL with the involved steps and partitioning processes.

• Attach to an instance of Database Engine.
• Open a New Query to write and create the partitioning script.

Write code to craft new filegroups, a precise partition function, and an explicit partition scheme and implement it. This example helps builds a new table with the partition scheme stated as the storage location.

-- Adds four new filegroups to the Hospital database  
ALTER DATABASE Hospital  
ADD FILEGROUP Cancer;  
GO  
ALTER DATABASE Hospital  
ADD FILEGROUP Surgery;  
GO  
ALTER DATABASE Hospital  
ADD FILEGROUP OPD;  
GO  
ALTER DATABASE Hospital  
ADD FILEGROUP Teaching;   

-- Adds one file for each filegroup.  
ALTER DATABASE Hospital   
ADD FILE   
(  
    NAME = CancerData,  
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL15.SQLEXPRESS\MSSQL\DATA\CancerData.ndf',  
    SIZE = 5MB,  
    MAXSIZE = 100MB,  
    FILEGROWTH = 5MB  
)  
TO FILEGROUP Cancer;  
ALTER DATABASE Hospital   
ADD FILE   
(  
    NAME = SurgeryData,  
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL15.SQLEXPRESS\MSSQL\DATA\SurgeryData.ndf',  
    SIZE = 5MB,  
    MAXSIZE = 100MB,  
    FILEGROWTH = 5MB  
)  
TO FILEGROUP Surgery;  
GO  
ALTER DATABASE Hospital   
ADD FILE   
(  
    NAME = OPDData,  
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL15.SQLEXPRESS\MSSQL\DATA\OPDData.ndf',  
    SIZE = 5MB,  
    MAXSIZE = 100MB,  
    FILEGROWTH = 5MB  
)  
TO FILEGROUP OPD;  
GO  
ALTER DATABASE Hospital   
ADD FILE   
(  
    NAME = TeachingData,  
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL15.SQLEXPRESS\MSSQL\DATA\TeachingData.ndf',  
    SIZE = 5MB,  
    MAXSIZE = 100MB,  
    FILEGROWTH = 5MB  
)  
TO FILEGROUP Teaching;  
GO

Creating the filegroups and adding files to each filegroup based on Departments

-- Creates a partition function called DepartmentPF that will partition the table into four partitions based on department ID  
CREATE PARTITION FUNCTION DepartmentPF (int)  
    AS RANGE LEFT FOR VALUES (101, 102, 103) ;  
GO

Creating partition function for dividing the table into four partitions

-- Creates a partition scheme called DepartmentRangePS that applies DepartmentPF to the four filegroups created above  
CREATE PARTITION SCHEME DepartmentRangePS  
    AS PARTITION DepartmentPF  
    TO (Cancer, Surgery, OPD, Teaching) ;  
GO

Creating partition scheme to apply partition function to the filegroups

-- Creates a partitioned table called PatientsPartitionTable that uses DepartmentRangePS to partition DeptID  
CREATE TABLE PatientsPartitionTable (patientID int , DeptID int , visitDate DateTime NOT NULL, PRIMARY KEY(patientID,DeptID))   
    ON DepartmentRangePS (DeptID) ;  
GO

Creating partitioned table

SELECT *   
FROM sys.tables AS t   
JOIN sys.indexes AS i   
    ON t.[object_id] = i.[object_id]   
    AND i.[type] IN (0,1)   
JOIN sys.partition_schemes ps   
    ON i.data_space_id = ps.data_space_id   
WHERE t.name = 'PatientsPartitionTable';   
GO

Checking if the table PatientsPartitionTable is partitioned

Partitioning a table by utilizing the SQL Server Management Studio partitioning wizard

Table partitioning can also be accomplished by the SQL Server Management Studio Partitioning Wizard, accessible in SQL Server 2008 onwards.

Step 1: Right-click on the specified table in the Object Explorer and in the Storage context menu and select the Create Partition command:

Step 2: Choosing the Create Partition preference opens the Create Partition Wizard.

Step 3: In the Select a Partitioning Column window, pick the partitioning column(s) from the obtainable columns:

Other choices right in the dialog comprise the Collocate of this table to the chosen partition table selection utilized to showcase the attached data sets to join with the partitioned column, and Storage Align Non-Unique Indexes as well as Unique Indexes with a particular Indexed Partition Column preference that aligns all the mentioned indexes of the partitioned table with the identical partition scheme.

Step 4: In the subsequent step, Select a Partition Function window, enter the specified partition function name and allow mapping of the table rows right into the partitions grounded and related to the partitioning column values, or pick an already present partition function:

Step 5: In the Select a Partition Scheme window, build the partition scheme for mapping the precise table partitions to diverse filegroups:

Step 6: Subsequent to the Map Partitions window, choose the partitioning range and pick the obtainable filegroups and the precise range boundary.

The Estimate storage selection regulates the Rowcount, the Essential space, and the Accessible space columns based on the detailed table records.

Step 7: The succeeding screen of the wizard provides the preference to implement the script swiftly or to save it. Once an option is chosen, it displays a review of selected assortments made in the wizard.

Step 8: Lastly, click the “Finish” button to end the entire process comprehensively.

What are the restrictions for partitioning utilizing SQL Server?

• If any rows have null values in the partitioning column(s) within a partition function, these rows are allocated to the left-most partition. However, if NULL is stated as a boundary value and RIGHT is directed, the left-most partition stays empty and NULL values are placed right in the second partition.
• In addition, CREATE TABLE approval in the database, ALTER approval on the precise scheme in which the table is being built, and forming a partitioned table needs further permissions. The permissions include ALTER ANY DATASPACE and CONTROL SERVER or ALTER ANY DATABASE approval right on the database server in which the partition function and partition scheme are being generated.

Automating the partition flow

• The database team has to track that the series of any partition function is concluding or not? To evade this manual job, users can better set up the SQL Server job to execute it automatedly.
• Automation with the partition job is even needed when the range of partition functions is not adequate to advance for the newly inserted data sets. 
• SQL Server job can be better implemented in a pre-defined scheduled time and assists in identifying the partition functions which are essential to be sustained further.
• SQL Server scheduler can be of great assistance with splitting a new partition range and addition of fresh filegroups as it is vital for precise partition functions and enabling schemes. 

Key Takeaways

We learned here how to use and build a partitioned table. We even explored partitioning a table by using the SQL Server Management Studio partitioning wizard.

Furthermore, we discovered that the partition series is always reliant on the precise row size right in the partition function. So, table partitioning in SQL Server is always useful and supportive for sustaining large tables.

Adding a new array to the partition function should now be an automated task. Empower your teams with powerful approaches to evade manual table activities of partition sustenance by enhancing and automating the processes.