Quiz for IS NULL

Q1: Which SQL operator checks for missing or undefined values?

A. = B. IS EMPTY C. IS NULL D. NOT IN

Q2: What does the IS NULL operator do in SQL?

A. Checks if a column has a NULL value B. Assigns a NULL value C. Deletes NULL values D. Replaces NULL with 0

Q3: Which SQL clause correctly finds all rows where the "email" column is NULL?

A. WHERE email IS NULL B. WHERE email = NULL C. WHERE email == NULL D. WHERE email <> NULL

Q4: What is the result of "NULL = NULL" in SQL?

A. TRUE B. FALSE C. NULL D. Syntax Error

Q5: How do you select rows where "last_name" is not null?

A. WHERE last_name != NULL B. WHERE last_name <> NULL C. WHERE last_name IS NOT NULL D. WHERE NOT last_name IS NULL

Q6: Which of the following is valid syntax to check for NULL?

A. column = NULL B. column IS NULL C. column == NULL D. column EQUALS NULL

Q7: What will "SELECT * FROM users WHERE age IS NULL" return?

A. Users with age 0 B. Users with unknown age C. All users D. Users with age > 0

Q8: Which statement filters out NULL values in a SELECT query?

A. WHERE column IS NULL B. WHERE column IS NOT NULL C. WHERE column = NULL D. WHERE column == NULL

Q9: Can NULL be used in numeric calculations in SQL?

A. Yes B. No C. Only with CAST D. Only with IF

Q10: What is the behavior of aggregate functions like SUM() on NULLs?

A. They skip NULLs B. They treat NULL as 0 C. They return NULL D. They throw error

Q11: Which function replaces NULL values with a default?

A. NVL() B. ISNULL() C. COALESCE() D. All of the above

Q12: What is the output of "NULL IS NULL"?

A. TRUE B. FALSE C. NULL D. Error

Q13: How to find all employees without a manager?

A. WHERE manager_id = NULL B. WHERE manager_id IS NULL C. WHERE manager_id == NULL D. WHERE NOT manager_id

Q14: Which SQL keyword is used with NULL to represent missing information?

A. DEFAULT B. NULLABLE C. NULL D. EMPTY

Q15: Is "NULL = NULL" the same as "IS NULL"?

A. Yes B. No C. Sometimes D. Only in Oracle

Q16: How to find products with no price assigned?

A. WHERE price IS NULL B. WHERE price = 0 C. WHERE price = NULL D. WHERE price IS EMPTY

Q17: What does IS NOT NULL return?

A. Rows with NULL values B. Rows with non-NULL values C. All rows D. Only blank strings

Q18: Which of the following can cause a column to have NULL?

A. Missing input B. Failed JOIN C. Uninitialized column D. All of the above

Q19: What is a common use of IS NULL in a LEFT JOIN?

A. To find non-matching records B. To filter NULLs C. To replace NULLs D. To check column type

Q20: How does a NULL affect ORDER BY clause?

A. It is sorted last by default B. It is sorted first by default C. It throws an error D. It is ignored

Q21: Can a primary key column be NULL?

A. Yes B. No C. Depends on DB D. Only once