A Unique Index in SQL ensures that the values in a column or combination of columns are unique across all rows. This quiz tests your understanding of how unique indexes work, when to use them, and how they differ from other index types.
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Which of the following is a valid SQL syntax to create a unique index?
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Question 3 of 15
3. Question
How many unique indexes can a table have?
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Question 4 of 15
4. Question
What will happen if you try to insert a duplicate value into a column with a unique index?
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Question 5 of 15
5. Question
What is the key difference between a unique index and a regular index?
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Question 6 of 15
6. Question
Which constraint in SQL automatically creates a unique index?
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Question 7 of 15
7. Question
Can a unique index be created on multiple columns?
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Question 8 of 15
8. Question
Can a unique index contain NULL values?
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Question 9 of 15
9. Question
When should you not use a unique index?
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Question 10 of 15
10. Question
Which is TRUE about unique indexes and performance?
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Question 11 of 15
11. Question
Which of the following automatically uses a unique index?
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Question 12 of 15
12. Question
Can you drop a unique index without dropping the column?
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Question 13 of 15
13. Question
Can a table have both a PRIMARY KEY and a UNIQUE index on different columns?
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Question 14 of 15
14. Question
Which of the following is a benefit of a unique index?
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Question 15 of 15
15. Question
Which query correctly creates a unique index on two columns – email and username?
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Summary
Unique indexes are critical for enforcing data integrity and preventing duplicates. This quiz on SQL unique index explores creation, behavior, performance, and usage scenarios of unique indexes in SQL databases.
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