HomeInterview QuestionsHave you used unique constraints in SQL?

Have you used unique constraints in SQL?

🟢 Easy Behavioral Junior level
1Times asked
May 2026Last seen
May 2026First seen

💡 Model Answer

Yes, I have used unique constraints to enforce data integrity. For instance, in a Customers table I added a UNIQUE constraint on the Email column to prevent duplicate email addresses. I also used composite unique constraints, such as combining FirstName, LastName, and BirthDate to ensure no duplicate personal records. These constraints are defined in the CREATE TABLE or ALTER TABLE statements and are enforced by the database engine.

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