MySQL Questions and Answers – Null: the Four Letter Word

This set of MySQL Multiple Choice Questions & Answers (MCQs) focuses on “Null: the Four Letter Word”.

1. What is the meaning of “NULL” in Mysql?
a) Not applicable
b) Value not yet known
c) Value undefined
d) All of the mentioned
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2. Is the following statement is true/false?
“An expression can be NULL, but can never equal to NULL”
a) True
b) False
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3. Is the following statement is true/false?
“Two NULL values are equal to each other”
a) True
b) False
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4. Which operator is used to check whether the expression is “NULL”?
a) IS NULL
b) NOT NULL
c) ON
d) None of the mentioned
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5. Which operator is used to check the expression is not “NULL”?
a) IS NULL
b) NOT NULL
c) ON
d) None of the mentioned
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6. What will be the output of the following MySQL command?

SELECT *
FROM person
WHERE emp_id IS NULL;

a) Only those rows where the emp_id column is NULL
b) Only those rows where the emp_id column is not NULL
c) No output
d) None of the mentioned
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7. What will be the output of the following MySQL command?

SELECT * 
FROM person
WHERE emp_id IS NOT NULL;

a) Only those rows where the emp_id column is NULL
b) Only those rows where the emp_id column is not NULL
c) No output
d) None of the mentioned
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8. What will be the output of the following MySQL command?

SELECT *
FROM person
WHERE emp_id = NULL;

a) Only those rows where the emp_id column is NULL
b) Only those rows where the emp_id column is not NULL
c) No output
d) None of the mentioned
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9. What will be the output of the following MySQL command?

SELECT fname
FROM person
WHERE emp_id != 6;

a) Only those names whose emp_id is not equal to 6
b) Only those names whose emp_id is equal to 6
c) No output
d) None of the mentioned
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10. What will be the output of the following MySQL command?

SELECT fname
FROM person
WHERE emp_id != 6 OR emp_id IS  NULL;

a) Only those names whose emp_id is not equal to 6 or emp_id with NULL values
b) Only those names whose emp_id is not equal to 6
c) Only those names whose emp_id is equal to 6
d) None of the mentioned
View Answer

Sanfoundry Global Education & Learning Series – MySQL Database.

To practice all areas of MySQL Database, here is complete set of 1000+ Multiple Choice Questions and Answers.