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Quiz on NULL Handling in SQL

by Quiz Orbit Team

In SQL, NULL represents missing, undefined, or unknown data. Handling NULLs correctly is crucial for accurate data retrieval, filtering, and comparison. This quiz tests your understanding of how SQL treats NULL values in queries, conditions, and functions.

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Question 1 of 15
1. Question
What does NULL mean in SQL?
- Zero
- Empty string
- Unknown or missing value
- Default value
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Question 2 of 15
2. Question
Which operator is used to check for NULL values in SQL?
- = NULL
- IS NULL
- == NULL
- NULL?
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Question 3 of 15
3. Question
What is the result of NULL = NULL in SQL?
- TRUE
- FALSE
- NULL
- Error
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Question 4 of 15
4. Question
How do you check if a column is not NULL?
- WHERE column <> NULL
- WHERE column IS NOT NULL
- WHERE column != NULL
- WHERE column NOT NULL
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Question 5 of 15
5. Question
Which of the following statements will return rows where salary is missing?
- WHERE salary = NULL
- WHERE salary IS NULL
- WHERE salary == NULL
- WHERE salary = ''
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Question 6 of 15
6. Question
What does the COALESCE() function do in SQL?
- Deletes NULLs
- Converts NULL to zero
- Returns the first non-NULL value
- Ignores NULLs in queries
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Question 7 of 15
7. Question
What is the result of this query: SELECT COALESCE(NULL, NULL, ‘SQL’);?
- NULL
- SQL
- Error
- Empty string
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Question 8 of 15
8. Question
Which function can be used to replace NULL with a custom value?
- NVL()
- REPLACE()
- CONCAT()
- COUNT()
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Question 9 of 15
9. Question
How does the COUNT() function treat NULLs?
- It counts them
- It throws an error
- It skips them
- It replaces them with 0
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Question 10 of 15
10. Question
What is returned by: SELECT COUNT(*) FROM employees;
- Count of non-null rows
- Count of NULL rows only
- Total number of rows including NULLs
- Count of columns
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Question 11 of 15
11. Question
In SQL, which comparison involving NULL returns TRUE?
- NULL = NULL
- NULL IS NULL
- NULL != NULL
- NULL >= NULL
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Question 12 of 15
12. Question
Which of the following will return 0 if the column contains NULL?
- SELECT COALESCE(NULL, 0);
- SELECT NULL + 0;
- SELECT IS NULL(NULL);
- SELECT COUNT(NULL);
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Question 13 of 15
13. Question
What is the default behavior of GROUP BY when NULLs are present?
- Ignores NULLs
- Treats NULLs as a separate group
- Converts NULLs to zeros
- Throws an error
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Question 14 of 15
14. Question
What happens when NULL is used in an arithmetic expression?
- Treated as 0
- Results in NULL
- Ignored
- Converted to blank
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Question 15 of 15
15. Question
Which function helps to avoid NULL-related issues in aggregate calculations?
- NVL()
- SUM()
- COALESCE()
- ROUND()
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Summary

This quiz on NULL Handling in SQL helps learners grasp how SQL treats missing values, and how functions like IS NULL, COALESCE, NVL, and COUNT behave when NULLs are involved. It’s essential for accurate data analysis and reporting.

Tags: null handling in sql quiz null handling quiz in sql quiz on null handling in sql quiz on sql null handling sql null handling quiz SQL Quiz

Quiz Orbit Team

At QuizOrbit, our team specializes in fun, informative quizzes across topics like general knowledge, technology, and entertainment. Boost your knowledge with our expert-designed quizzes.

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