Adventures in Machine Learning

Boost Query Performance with SQL Server Indexes and Included Columns

Improving Query Performance with Indexes and Included Columns

Are you experiencing slow running queries? Do you need a way to improve query performance?

SQL Server indexes with included columns could be the solution to your problem. In this article, we will explain how using indexes with included columns can boost your query performance and provide you with an overview of key lookup and nested loops.

We will also provide you with practical tips on creating an index with included columns to help you write more efficient queries.to SQL Server Indexes with Included Columns

SQL Server indexes are essential for improving query performance, but they can be challenging to configure. One of the most effective ways to optimize query performance is to use an index with included columns.

SQL Server indexes with included columns are a type of non-clustered index that allows you to add non-key columns to your index, making queries faster and more efficient.

Key Lookup and Nested Loops

A key lookup occurs when SQL Server uses an index to locate the data required by a query, but it needs to reference the underlying table to retrieve additional data. A key lookup adds an additional operation, which can result in slower query performance, especially when dealing with larger datasets.

On the other hand, nested loops are a type of join operation that use an index to retrieve data from one table and then loop through a second table to match the index values. Nested loops are quick when dealing with small datasets, but they can suffer performance issues with larger tables.

Creating an Index with Included Columns

Creating an index with included columns is a relatively simple process that can have a significant impact on query performance. To create an index with included columns, you need to specify the index type as non-clustered, specify the table and columns you want to index, and then add the included column.

Syntax for

Creating an Index with Included Columns

The syntax for creating an index with included columns in SQL Server is simple. You need to use the following syntax:

CREATE NONCLUSTERED INDEX IndexName

ON TableName (IndexedColumns)

INCLUDE (IncludedColumns)

An example of creating an index with included columns on the Customer table is as follows:

CREATE NONCLUSTERED INDEX IX_Customer_City

ON Customer (City)

INCLUDE (FirstName, LastName)

The above code creates a non-clustered index on the City column of the Customers table and adds the FirstName and LastName columns as included columns.

Benefits of Using Indexes with Included Columns

Improved Query Performance

The primary benefit of using indexes with included columns is that it improves query performance. Indexes with included columns reduce the number of key lookups that SQL Server has to perform, resulting in faster query execution times.

It also means that the SQL Server engine has to perform fewer I/O operations, resulting in reduced server load and faster query response times. Fewer Disk I/O Operations

Indexes with included columns reduce the number of disk I/O operations required by SQL Server.

Disk I/O operations are responsible for accessing data on disk, and the more disk I/O operations required, the slower the query performance. By including additional columns in the index, you can reduce the number of disk I/O operations required by SQL Server, resulting in faster query execution times.

Covering Queries with Non-Clustered Indexes

Another advantage of using indexes with included columns is that it can make your queries covering queries. Covering queries are queries that can retrieve all the required columns from the index itself without having to reference the underlying table.

As a result, covering queries require fewer disk I/O operations and can result in significant performance improvements.

Conclusion

In conclusion, indexes with included columns are an effective way to improve query performance in SQL Server. By reducing the number of key lookups and disk I/O operations, these indexes can speed up query execution times.

Moreover, covering queries can also offer significant performance benefits. Understanding how to create and implement indexes with included columns can be a valuable tool for developers tasked with optimizing query performance in SQL Server.

Using Included Columns in a SQL Server Index

In this article, we will explore the benefits of using included columns when creating a non-clustered index in SQL Server. We will use a sample database and the Sales.Customers table to illustrate how included columns can improve query performance.

We will provide examples of creating the initial index, the query using the initial index, creating an index with included columns, and the query using an index with included columns. Sample Database and Sales.Customers Table

For our examples, we will use the AdventureWorks sample database by Microsoft.

Within this database, the Sales.Customers table stores customer information such as customer ID, first name, last name, and email address. Our goal is to improve query performance when searching for customers by email address.

Creating the Initial Index for the Email Column

To start, we will create an initial non-clustered index on the email column in the Sales.Customers table. We can do this using the following SQL command:

CREATE NONCLUSTERED INDEX IX_Sales_Customers_Email

ON Sales.Customers (Email);

This command creates a new non-clustered index named “IX_Sales_Customers_Email” on the email column within the Sales.Customers table. This index should improve query performance when searching for customers by email address as all matching records are quickly located.

Query using the Initial Index

After creating the initial index on the email column, we can execute a simple query to test its performance. We will search for a customer with the email address “[email protected]”:

SELECT *

FROM Sales.Customers

WHERE Email = ‘[email protected]

With the initial index, this query should perform well as the email column is indexed.

However, if we attempt a more complex search that relies on additional details, then the query performance will likely suffer.

Creating an Index with Included Columns

To enhance query performance when there are multiple search criteria involved, we can create an index with included columns. In addition to indexing the email column, we can specify additional columns to include within the index.

This will result in a more effective index that can return results more quickly. We can create an index with included columns using the following SQL command:

CREATE NONCLUSTERED INDEX IX_Sales_Customers_Email_Included

ON Sales.Customers (Email)

INCLUDE (FirstName, LastName);

As you can see, we have created a non-clustered index called “IX_Sales_Customers_Email_Included” on the email column, with FirstName and LastName included within the index.

Query using Index with Included Columns

Now let’s run our query using the new index with included columns:

SELECT *

FROM Sales.Customers

WHERE Email = ‘[email protected]

AND FirstName = ‘Linda’

AND LastName = ‘Mitchell’

With the index that includes FirstName and LastName, this query should perform much better than the initial index as all necessary columns are now indexed.

Syntax for Creating Non-Clustered Index with Included Columns

To create a non-clustered index with included columns, we need to use a slightly modified version of the CREATE NONCLUSTERED INDEX command. We can begin by creating a non-clustered index just like before with the following SQL command:

CREATE NONCLUSTERED INDEX IX_IndexName

ON TableName (IndexedColumns)

However, to include additional columns within the index, we need to modify the command by specifying the included columns:

CREATE NONCLUSTERED INDEX IX_IndexName

ON TableName (IndexedColumns)

INCLUDE (IncludedColumns)

Example

Syntax for Creating Non-Clustered Index with Included Columns

To create an index with included columns on the Sales.Customers table, we would use the following SQL command:

CREATE NONCLUSTERED INDEX IX_Sales_Customers_Email_FirstName_LastName

ON Sales.Customers (Email)

INCLUDE (FirstName, LastName)

This command creates a new non-clustered index named “IX_Sales_Customers_Email_FirstName_LastName” on the email column, including the FirstName and LastName columns as additional included columns. This index should dramatically improve query performance when searching for customers by email, first name or last name.

Conclusion

In conclusion, included columns are an important tool for optimizing query performance in SQL Server. By creating indexes with included columns, you can reduce the number of key lookups and disk I/O operations required by SQL Server.

Further, this can speed up query execution times and improve query performance. Understanding how to create and implement indexes with included columns can make it easier to optimize query performance in SQL Server.

In this article, we explored the benefits of using included columns when creating a non-clustered index in SQL Server. By creating an index with included columns, you can improve query performance by reducing the number of key lookups and disk I/O operations required by SQL Server.

Further, this approach can speed up query execution times and make it easier to optimize query performance in SQL Server. The main points of the article were creating an initial index, querying it, creating an index with included columns, and querying it again.

From these examples, you can see how included columns can enhance query performance. Overall, understanding how to create and implement indexes with included columns is an essential tool for developers tasked with optimizing query performance in SQL Server.

Popular Posts