Today, we will explore a common question that often arises when working with SQL Server: What is the difference between ORIGINAL_LOGIN() and SUSER_SNAME() and when should we use them?

The function ORIGINAL_LOGIN() returns the name of the original or very first login that connected to the instance of SQL Server. It is primarily used to identify the original login in sessions. This feature can be particularly useful for auditing purposes in applications or databases where context switching occurs frequently.

Let’s take a look at a quick T-SQL example to understand how ORIGINAL_LOGIN() works:

USE AdventureWorks2012;
GO

-- Get Login Details
SELECT ORIGINAL_LOGIN() AS OriginalLogin, SUSER_SNAME() AS CurrentLogin;
GO

-- Create a temporary login and user.
CREATE LOGIN TestLogin WITH PASSWORD = 'Complex@1';
CREATE USER TestUser FOR LOGIN TestLogin;
GO

-- Execute as another user
EXECUTE AS LOGIN = 'TestLogin';
GO

-- Get Login Details
SELECT ORIGINAL_LOGIN() AS OriginalLogin, SUSER_SNAME() AS CurrentLogin;
GO

-- Revert Execution as another user
REVERT;
GO

-- Get Login Details
SELECT ORIGINAL_LOGIN() AS OriginalLogin, SUSER_SNAME() AS CurrentLogin;
GO

-- Clean up
DROP LOGIN TestLogin;
DROP USER TestUser;
GO

In the above example, we first retrieve the current user and original login, and you will notice that they are the same. Then, we create a new user and set the execution context to the new user. When we run the same command again, you will notice that the current user name has changed, but the original login remains the same.

By using ORIGINAL_LOGIN(), we can easily track the original user associated with a session, making it a valuable tool for auditing purposes. It allows us to identify who the original user was, even if there have been multiple context switches within the session.

Now, let’s discuss some real-world use cases for ORIGINAL_LOGIN().

One common scenario is when you have an application that requires frequent context switching between different users. In such cases, ORIGINAL_LOGIN() can help you keep track of the original user who initiated the session, providing valuable information for auditing and security purposes.

For example, let’s say you have a multi-tenant application where each tenant has their own database. When a user logs in, the application connects to the respective tenant’s database using a shared login. However, within the session, the application switches the context to the specific user associated with that tenant. By using ORIGINAL_LOGIN(), you can easily identify the original tenant’s login, even if the context has been switched multiple times.

Overall, ORIGINAL_LOGIN() is a powerful function that can greatly enhance your auditing capabilities and provide valuable insights into the original user associated with a session.

So, the next time you are working on an application that involves context switching or requires auditing, consider utilizing ORIGINAL_LOGIN() to track the original user and ensure the security and integrity of your SQL Server environment.

Do you currently use ORIGINAL_LOGIN() in your applications? What other use cases can you think of for this feature? Share your thoughts in the comments below!