What is SQL Server Language Extensions?

Applies to: yesSQL Server (all supported versions)

Language Extensions is a feature of SQL Server used for executing external code. The relational data can be used in the external code using the extensibility framework.

In SQL Server 2019, Java is supported. The default Java runtime is Zulu Open JRE. You can also use another Java JRE or SDK.

What you can do with Language Extensions

Language Extensions uses the extensibility framework for executing external code. Code execution is isolated from the core engine processes, but fully integrated with SQL Server query execution. They let you execute code where the data resides, eliminating the need to pull data across the network.

External languages are defined with CREATE EXTERNAL LANGUAGE. The system stored procedure sp_execute_external_script is used as the interface for executing the code.

Language Extensions provides multiple advantages:

  • Data security. Bringing external language execution closer to the source of data avoids wasteful or insecure data movement.
  • Speed. Databases are optimized for set-based operations. Recent innovations in databases such as in-memory tables make summaries and aggregations lightning, and are a perfect complement to data science.
  • Ease of deployment and integration. SQL Server is the central point of operations for many other data management tasks and applications. By using data that resides in the database, you ensure that the data used by Java is consistent and up-to-date.

How to get started

Step 1: Install the software

Step 2: Configure a development tool

Developers typically write code on their own laptop or development workstation. With language extensions in SQL Server, there is no need to change this process. After installation is complete, you can run Java code on SQL Server.

Step 3: Write your first code

Execute Java code from within T-SQL script:


  • The number of values in input and output buffers cannot exceed MAX_INT (2^31-1) since that is the maximum number of elements that can be allocated in an array in Java.

Next steps