NULL in AND, OR, NOT logic in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select rows where the condition is TRUE or UNKNOWN using OR.

SQL

SELECT * FROM employees WHERE active = TRUE [1] salary > 50000;

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

ANOT

B=

COR

DAND

Attempts:

3 left

💡 Hint

Common Mistakes

Using AND instead of OR causes rows with NULL to be excluded.

Using = instead of logical operators.

Using OR returns TRUE if either condition is TRUE or UNKNOWN (NULL treated as UNKNOWN).

2fill in blank

medium

Complete the code to find rows where NOT condition is TRUE.

SQL

SELECT * FROM orders WHERE NOT (shipped_date IS NULL) [1] status = 'pending';

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

ANOT

B=

COR

DAND

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR causes rows to be included even if NOT condition is FALSE.

Using NOT again causes double negation.

Use AND to combine NOT condition with another condition that must also be TRUE.

3fill in blank

hard

Fix the error in the WHERE clause to correctly handle NULL with AND.

SQL

SELECT * FROM products WHERE price > 100 [1] discount IS NULL;

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

AAND

BOR

CNOT

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR includes rows where price > 100 but discount is not NULL.

Using = causes syntax error with IS NULL.

Use AND to ensure both conditions must be TRUE, including NULL check.

4fill in blank

hard

Fill both blanks to select rows where either condition is TRUE or the other is NOT TRUE.

SQL

SELECT * FROM sales WHERE region = 'East' [1] amount > 1000 [2] NOT (discount IS NULL);

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

AOR

BAND

CAND NOT

DNOT

Attempts:

3 left

💡 Hint

Common Mistakes

Using AND in first blank excludes rows unnecessarily.

Using NOT alone causes syntax errors.

Use OR to allow either condition, and AND to combine with NOT condition properly.

5fill in blank

hard

Fill all three blanks to create a condition that excludes NULLs and selects rows with amount > 500 or status 'active'.

SQL

SELECT * FROM transactions WHERE amount IS NOT [1] AND (amount [2] 500 [3] status = 'active');

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

ANULL

B>

COR

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using = NULL instead of IS NOT NULL.

Using AND instead of OR in the last blank.

Use IS NOT NULL to exclude NULLs, > to compare amount, and OR to allow status 'active'.