NULLIF function in MySQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return NULL if the two values are equal.

MySQL

SELECT NULLIF(10, [1]);

Drag options to blanks, or click blank then click option'

A5

B10

C15

D20

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a different number than the first argument will return the first argument instead of NULL.

The NULLIF function returns NULL if both arguments are equal. Here, 10 equals 10, so the result is NULL.

2fill in blank

medium

Complete the code to return the second value if the first is not equal to it.

MySQL

SELECT NULLIF(5, [1]);

Drag options to blanks, or click blank then click option'

ANULL

B5

C10

D5.0

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing the same value as the first argument will return NULL, not the first argument.

NULLIF returns the first argument if it is not equal to the second. Here, 5 is not equal to 10, so it returns 5.

3fill in blank

hard

Fix the error in the code to correctly use NULLIF with column names.

MySQL

SELECT NULLIF(price, [1]) FROM products;

Drag options to blanks, or click blank then click option'

Aprice

BNULL

C'price'

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Putting column names in single quotes treats them as strings, causing errors or wrong results.

Column names should not be in quotes. Using price without quotes refers to the column correctly.

4fill in blank

hard

Fill both blanks to return NULL if quantity equals 0, else return quantity.

MySQL

SELECT NULLIF([1], [2]) AS result FROM inventory;

Drag options to blanks, or click blank then click option'

Aquantity

B0

CNULL

D'0'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '0' as a string instead of 0 as a number.

Using NULL as the second argument, which is invalid.

NULLIF(quantity, 0) returns NULL if quantity is 0, else returns quantity.

5fill in blank

hard

Fill all three blanks to return NULL if status equals 'inactive', else return status in uppercase.

MySQL

SELECT NULLIF(UPPER([1]), [2]) AS status_upper FROM users WHERE [3] = 'inactive';

Drag options to blanks, or click blank then click option'

Astatus

B'INACTIVE'

D'inactive'

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'inactive' in NULLIF comparison causes mismatch.

Using quotes incorrectly around column names.

We convert status to uppercase and compare it to 'INACTIVE' to return NULL if equal. The WHERE clause filters rows where status is 'inactive'.