IFNULL and COALESCE in MySQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return the value of 'score' or 0 if it is NULL.

MySQL

SELECT IFNULL(score, [1]) AS result FROM games;

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

A0

BNULL

Cscore

D''

Attempts:

3 left

💡 Hint

Common Mistakes

Using NULL as the replacement value, which does not change NULL results.

Using the column name again instead of a default value.

The IFNULL function returns the first argument if it is not NULL; otherwise, it returns the second argument. Here, if 'score' is NULL, it returns 0.

2fill in blank

medium

Complete the code to return the first non-NULL value among 'nickname', 'username', or 'guest'.

MySQL

SELECT COALESCE(nickname, username, [1]) AS display_name FROM users;

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

A'username'

BNULL

Cnickname

D'guest'

Attempts:

3 left

💡 Hint

Common Mistakes

Using NULL as the last value, which does not provide a fallback.

Using column names instead of a string literal for the fallback.

COALESCE returns the first non-NULL value from the list. If both 'nickname' and 'username' are NULL, it returns 'guest'.

3fill in blank

hard

Complete the code to return the value of 'price' or 100 if it is NULL.

MySQL

SELECT IFNULL(price, [1]) AS final_price FROM products;

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

A100

Bprice

CNULL

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using NULL as the replacement value, which does not change NULL results.

Using the column name again instead of a default value.

The IFNULL function returns the first argument if it is not NULL; otherwise, it returns the second argument. Here, if 'price' is NULL, it returns 100.

4fill in blank

hard

Fill both blanks to create a dictionary of words and their lengths only if length is greater than 3.

MySQL

SELECT word, LENGTH(word) AS length FROM words WHERE LENGTH(word) [1] [2];

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

A>

B<

C3

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' reverses the condition.

Using 5 instead of 3 changes the filter.

The query selects words where the length is greater than 3. So the operator is '>' and the number is 3.

5fill in blank

hard

Fill all three blanks to select the first non-NULL email from 'email1', 'email2', or 'email3'.

MySQL

SELECT COALESCE([1], [2], [3]) AS contact_email FROM contacts;

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

Aemail1

Bemail2

Cemail3

Demail4

Attempts:

3 left

💡 Hint

Common Mistakes

Including a non-existent column like 'email4'.

Repeating the same column multiple times.

COALESCE returns the first non-NULL value among the given columns. Here, it checks 'email1', then 'email2', then 'email3'.