INTERSECT and EXCEPT in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find common customers in both tables.

PostgreSQL

SELECT customer_id FROM orders_2023 [1] SELECT customer_id FROM orders_2024;

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

AINTERSECT

BUNION

CEXCEPT

DJOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNION returns all unique rows from both tables, not just common ones.

Using EXCEPT returns rows from the first query that are not in the second.

The INTERSECT keyword returns rows common to both queries.

2fill in blank

medium

Complete the code to find customers who ordered in 2023 but not in 2024.

PostgreSQL

SELECT customer_id FROM orders_2023 [1] SELECT customer_id FROM orders_2024;

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

AEXCEPT

BINTERSECT

CUNION

DJOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using INTERSECT returns only common rows, not unique ones.

Using UNION combines all unique rows from both queries.

The EXCEPT keyword returns rows from the first query that are not in the second.

3fill in blank

hard

Fix the error in the query to find customers who ordered in 2024 but not in 2023.

PostgreSQL

SELECT customer_id FROM orders_2024 [1] SELECT customer_id FROM orders_2023;

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

AINTERSECT

BJOIN

CEXCEPT

DUNION ALL

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNION ALL returns all rows including duplicates.

Using INTERSECT returns only common rows.

To find customers in 2024 but not in 2023, use EXCEPT with 2024 first.

4fill in blank

hard

Fill both blanks to find customers who ordered in 2023 or 2024 but not both.

PostgreSQL

SELECT customer_id FROM orders_2023 [1] SELECT customer_id FROM orders_2024
EXCEPT
SELECT customer_id FROM orders_2023 [2] SELECT customer_id FROM orders_2024;

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

AUNION

BINTERSECT

CEXCEPT

DJOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using EXCEPT instead of UNION in the first blank returns only unique to 2023.

Using UNION instead of INTERSECT in the second blank does not exclude common customers.

This query finds customers in either year but excludes those in both by subtracting the INTERSECT from the UNION.

5fill in blank

hard

Fill all three blanks to find customers who ordered in 2023 but not in 2024, showing their names and IDs.

PostgreSQL

SELECT [1], customer_id FROM customers WHERE customer_id IN (
  SELECT customer_id FROM orders_2023 [2] SELECT customer_id FROM orders_2024
) [3] ORDER BY customer_id;

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

Acustomer_name

BEXCEPT

CLIMIT 10

DWHERE

Attempts:

3 left

💡 Hint

Common Mistakes

Using WHERE instead of LIMIT causes syntax errors at the end.

Using INTERSECT instead of EXCEPT returns common customers, not unique ones.

This query selects customer names and IDs for those who ordered in 2023 but not 2024, limiting results to 10.