Answer.

SQL Server supports a multi-level permission system through roles, user permissions (GRANT/REVOKE), and schemas. Key principles:

• Assign a role= a set of permissions that the user will receive later.
• Give minimal permissions, only necessary (principle of least privilege).
• Separate permissions at the database, table, view, and procedure levels.
• For particularly important operations, use only stored procedures or views, not direct access to tables.

Example of creating roles and assigning permissions:

-- Create a role for analysts
CREATE ROLE Analyst;
-- Grant only SELECT on necessary tables
GRANT SELECT ON Sales TO Analyst;
-- Prohibit data modification
REVOKE INSERT, UPDATE, DELETE ON Sales FROM Analyst;
-- Assign the role to a user
GRANT Analyst TO user_ivan;

Often, roles are distinguished for reading (read-only), modification, administration, and specific operations.

Trick question.

Trick: "Can a user with access only to a view (VIEW) modify the underlying table through it? Provide an example."

Answer: Yes, if the VIEW does not contain aggregation/grouping and is not read-only (WITH CHECK OPTION) – INSERT/UPDATE/DELETE can be performed on the VIEW, and changes will affect the underlying table if permissions allow.

-- A view trimming unnecessary columns
CREATE VIEW SalesAsView AS SELECT id, total, manager_id FROM Sales;
-- If allowed, the user will make changes like this:
UPDATE SalesAsView SET total=1000 WHERE id=42;
-- This will affect Sales.total for id=42

Solution: use readonly VIEWs or prohibit data modification rights through views.

Examples of real mistakes due to ignorance of the topic's subtleties.

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Story

Project: HR portal, personal data of employees.

Mistake: Operators had access to the underlying table through VIEW without restriction on UPDATE — accidentally modified each other's salaries, although the VIEW was initially intended "for reporting only".

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Story

Project: Accounting, external integrations.

Mistake: Granted the external system rights INSERT and SELECT on the entire DB instead of only INSERT in the necessary tables. Result: vulnerability to reading the entire DB and possible violation of GDPR legislation.

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Story

Project: SaaS platform, multi-user reports.

Mistake: All clients worked in one schema with shared rights: accidentally saw and could edit each other's data. Solution — segmentation into schemas, separate roles, and individual restrictions at the Row Level Security (RLS) level.

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