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Data & Analytics · Intermediate

Dynamic Data Masking (DDM)

Masking sensitive column values in query results for unauthorized users at run time without changing the stored data.

Definition

SQL Server and Azure SQL DDM offer default, email, random and custom string masks, and users with UNMASK see real values. It is not a strong security boundary, because inference attacks remain possible. Snowflake implements DDM with masking policies.

Example

ALTER TABLE Customers ALTER COLUMN Email ADD MASKED WITH (FUNCTION = 'email()');

Exam tip

DDM obscures data in results only; it is not encryption and doesn't stop privileged users.

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