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Home Forums Implement row-level security in SQL Server to restrict access to data to users. – MindStick
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1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 12 Jul 2024
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Row-level security (RLS) in SQL Server allows you to control access to rows in a database table based on the characteristics of the user executing a query. 

Here's a step-by-step guide on how to implement RLS:

1. Create the Main Table

Create a table to store the data.

CREATE TABLE Sales (
    SaleID INT PRIMARY KEY,
    SaleAmount DECIMAL(10, 2),
    SalesPersonID INT,
    SaleDate DATE
);

2. Create a Security Predicate Function

Create an inline table-valued function that returns a row if the user is authorized to view it.

CREATE FUNCTION dbo.SalesPersonFilter(@SalesPersonID INT)
RETURNS TABLE
WITH SCHEMABINDING
AS
RETURN SELECT 1 AS result
WHERE @SalesPersonID = CAST(SESSION_CONTEXT(N'SalesPersonID') AS INT);

3. Create a Security Policy

Create a security policy that binds the security predicate function to the table.

CREATE SECURITY POLICY SalesFilterPolicy
ADD FILTER PREDICATE dbo.SalesPersonFilter(SalesPersonID)
ON dbo.Sales
WITH (STATE = ON);

4. Set Up User Context

Use SESSION_CONTEXT to set the user context when a user logs in or a session starts. This should be done by your application or within your session.

-- Example of setting the session context for a SalesPerson with ID 1
EXEC sp_set_session_context @key = N'SalesPersonID', @value = 1;

5. Test the Implementation

Insert some sample data and test the row-level security.

-- Insert sample data
INSERT INTO Sales (SaleID, SaleAmount, SalesPersonID, SaleDate)
VALUES
(1, 100.00, 1, '2024-01-01'),
(2, 200.00, 2, '2024-01-02'),
(3, 300.00, 1, '2024-01-03');

-- Set session context for SalesPersonID 1
EXEC sp_set_session_context @key = N'SalesPersonID', @value = 1;

-- Test query as SalesPersonID 1
SELECT * FROM Sales;

Example Output:

SaleID SaleAmount SalesPersonID SaleDate
1 100.0 1 2024-01-01
3 300.0 1 2024-01-03


In this example, the SalesPersonID 1 can only see their own sales data. Other sales data (e.g., SalesPersonID 2) are not visible.

Considerations

  • Ensure that the security policy and predicate function are created with SCHEMABINDING.
  • The application must set them SESSION_CONTEXT correctly based on the authenticated user.
  • Review and test the security policies thoroughly to ensure they meet the security requirements.
  • Use database roles and permissions to further secure the implementation.

By implementing RLS, you can effectively control access to rows in a table, ensuring that users only see the data they're authorized to view.

Read more

Write a basic SELECT statement to retrieve data from a SQL Server table.

write a query to n-th highest salary.

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