Implementing Row-Level Security in SQL Server

Introduction

Row-Level Security (RLS) is a feature in SQL Server that enables you to control access to rows in a database table based on user permissions. This guide explores the implementation of RLS in SQL Server.

1. Enabling RLS

To use RLS, you need to enable the feature on your SQL Server database. Execute the following code to enable RLS for your database.

-- Enable RLS for the database
ALTER DATABASE YourDatabaseName SET ENABLE_RLS = ON;
    

2. Creating Security Policies

Security policies define the rules that control access to rows in a table. Each policy specifies a predicate that determines which rows a user can access.

-- Create a security policy
CREATE SECURITY POLICY SalesPolicy
ADD FILTER PREDICATE SalesFilter(UserId) ON Sales
WITH (STATE = ON);
    

3. Defining Predicate Functions

Predicate functions determine which rows a user can access. You can create custom functions that return a boolean result based on your criteria.

-- Create a predicate function
CREATE FUNCTION SalesFilter(@UserId AS UNIQUEIDENTIFIER)
RETURNS TABLE
WITH SCHEMABINDING
AS
    RETURN SELECT 1 AS Result
    WHERE @UserId = USER_ID();
    

4. Testing Row-Level Security

To test RLS, create users and assign them to the appropriate roles. Then, test data access based on the security policies you've defined.

-- Create a user and assign to a role
CREATE USER JohnSmith FOR LOGIN JohnSmith;
EXEC sp_addrolemember 'SalesRole', 'JohnSmith';
-- Test data access
EXECUTE AS USER = 'JohnSmith';
SELECT * FROM Sales;
REVERT;
    

Conclusion

Implementing Row-Level Security in SQL Server is a powerful feature for controlling access to rows in a database table. By enabling RLS, creating security policies, defining predicate functions, and testing the security policies, you can ensure that data access is restricted according to your business rules.