What is SQL Linked Server?

Hi Dev, are you curious about how to link servers in SQL? Well, you’ve come to the right place. In this article, we will discuss SQL Linked Server and its importance in SQL Server. Let’s dive in!

Introduction

SQL Linked Server is an essential tool for connecting one SQL Server instance to another. With Linked Server, you can access data from one server as if it is located on the same server instance. It enables you to query data from different data sources without having to migrate the data to a single location.

Linked Server is an invaluable feature of SQL Server that minimizes the need for migration, replication and enables querying of multiple data sources. By using Linked Server, you can quickly perform data integration on multiple data sources, making the data access process more efficient.

How Does SQL Linked Server Work?

To understand how SQL Linked Server works, you need to know what happens when you execute a query in SQL Server. A query is parsed, optimized, and executed by the SQL Server Database Engine.

When a query requires data that’s not located in the same SQL Server instance as the query, SQL Server initiates a remote procedure call (RPC) to the remote server. The RPC includes the query that the remote server must execute, and the remote server responds with the result set.

The Linked Server feature enables the Database Engine to execute queries that access data from external data sources using the same mechanism that it uses to access data in the local SQL Server instance.

The Linked Server feature creates a logical connection between two SQL Server instances, enabling the use of distributed queries. By using this feature, you can query data from different data sources, including Oracle, MySQL, and PostgreSQL.

Setting Up SQL Linked Server

The process of setting up a Linked Server is straightforward. You can use SQL Server Management Studio (SSMS) to set up a Linked Server.

The first step is to establish a connection to the server to which you want to link. Once the connection is established, you need to create a new Linked Server object by navigating to the Server Objects folder in SSMS and selecting the Linked Servers folder.

You then need to provide a name for the Linked Server, the server type, and the server name or IP address. You can also specify the login credentials that the Linked Server should use to connect to the remote server.

After you have created the Linked Server object, you can start executing distributed queries. To execute a distributed query, you need to qualify the table name with the Linked Server name, as shown in the following example:

Example
SELECT * FROM [LinkedServerName].[DatabaseName].[SchemaName].[TableName]

Advantages of SQL Linked Server

SQL Linked Server offers several advantages:

Efficiency:

Linked Server enables you to access data from different data sources without having to migrate the data. This feature saves you time and resources by enabling you to execute distributed queries that span multiple data sources.

Flexibility:

The feature supports a wide range of data sources, including Oracle, MySQL, PostgreSQL, and more. This flexibility enables you to use SQL Server as a single access point to all your data sources.

Simplicity:

Linked Server is easy to set up and use. Once you’ve set up the connection to the remote server, you can start executing distributed queries.

FAQ

What are the prerequisites for setting up SQL Linked Servers?

The prerequisites for setting up Linked Servers are a working knowledge of SQL Server, access to both the local and remote SQL Server instances, and sufficient permissions to create and manage Linked Server objects.

Can I use Linked Server to access non-SQL data sources?

Yes, you can use Linked Server to access non-SQL data sources, including Oracle, MySQL, and PostgreSQL.

Is Linked Server secure?

Linked Server can be secure if you use the appropriate authentication mechanisms and encrypt the data transfer process between the local and remote SQL Server instances.

Can I use Linked Server for replication?

Yes, you can use Linked Server for replication. By creating a Distributed Availability Group, you can replicate data between two SQL Server instances, even if they are located in different data centers.

Conclusion

In conclusion, SQL Linked Server is a valuable feature that enables you to access data from multiple data sources using SQL Server as a single access point. By using Linked Server, you can query data from different data sources without having to migrate the data to a single location. It’s also easy to set up and use, making it a great tool for data integration and optimization.