To enable row-level security (RLS) in MS SQL Server (2016 and later), you need to define a security policy that uses a user-defined, inline table-valued function as a filter predicate.
Step-by-Step Guide
1. Ensure compatibility
Verify that your SQL Server instance is at least SQL Server 2016 or newer.
2. Create a schema for RLS objects (Recommended)
This practice separates your security logic from the application data.
CREATE SCHEMA Security;
GO
3. Create a predicate function
This inline table-valued function contains the logic for determining which rows a user can access. The function must be created with SCHEMABINDING.
Example: This function allows a user to see rows where the UserID column matches their username, or if they are a Manager.
CREATE FUNCTION Security.fn_securitypredicate(@UserID AS sysname)
RETURNS TABLE
WITH SCHEMABINDING
AS
RETURN SELECT 1 AS result
WHERE @UserID = USER_NAME() OR USER_NAME() = 'Manager';
GO
4. Create and enable a security policy
The security policy links the predicate function to your target table and enables the RLS enforcement.
Example: This policy applies the function to the dbo.YourTable table, using the UserID column for the filter.
CREATE SECURITY POLICY SecurityPolicy
ADD FILTER PREDICATE Security.fn_securitypredicate(UserID) ON dbo.YourTable
WITH (STATE = ON);
GO
5. Grant necessary permissions
Ensure users have SELECT permission on both the target table and the security function.
GRANT SELECT ON dbo.YourTable TO SalesRep1;
GRANT SELECT ON Security.fn_securitypredicate TO SalesRep1;
-- Repeat for other users/roles as needed
Testing the ImplementationYou can test RLS by impersonating different users to verify they only see authorized data.