Practice - UNIQUE Constraint
Practice Questions
Test your understanding with targeted questions
What is the purpose of the UNIQUE constraint in SQL?
💡 Hint: Think about data consistency and duplicate prevention.
Can a column with a UNIQUE constraint accept NULL values?
💡 Hint: Consider how primary keys differ.
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Interactive Quizzes
Quick quizzes to reinforce your learning
What does the UNIQUE constraint ensure for a database column?
💡 Hint: Think about its primary role in data management.
True or False: A UNIQUE constraint can ignore NULL values.
💡 Hint: Consider how NULL differs from regular values.
1 more question available
Challenge Problems
Push your limits with advanced challenges
Design a table for an online forum that uses a UNIQUE constraint on both usernames and emails while ensuring that only one of the fields can be NULL.
💡 Hint: Consider how you would enforce uniqueness while allowing NULL for one of the fields.
Write a SQL command to add a UNIQUE constraint to an existing Products table for the SKU column. Ensure to describe any potential impacts.
💡 Hint: Think about how constraints are added to already existing tables.
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Reference links
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