Which constraint ensures that every value in a specific column is unique across all rows in that table, but still permits a NULL value? MCQ with Answer and Explanation
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Question #1
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In SQL, what does the 'IS NULL' operator check?
Correct Answer: Option B
Explanation:
IS NULL is used to test for NULL values, because NULL is not equal to anything.
IS NULL is used to test for NULL values, because NULL is not equal to anything.
This question belongs to:
Computer
Database Management System (DBMS)
Question #2
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What is a domain in the context of the relational model?
Correct Answer: Option D
Explanation:
A domain defines the set of permissible values that an attribute can take, ensuring data consistency.
A domain defines the set of permissible values that an attribute can take, ensuring data consistency.
This question belongs to:
Computer
Database Management System (DBMS)
Question #3
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In SQL, how do you check if a value is NOT NULL?
Correct Answer: Option C
Explanation:
IS NOT NULL is the correct operator to test for non-NULL values.
IS NOT NULL is the correct operator to test for non-NULL values.
This question belongs to:
Computer
Database Management System (DBMS)
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