Multiple CTEs in one query in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a CTE block.

PostgreSQL

WITH [1] AS (SELECT * FROM employees)

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

AWITH

BSELECT

CFROM

DJOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using SELECT instead of WITH to start a CTE.

Confusing FROM with the CTE start keyword.

The WITH keyword starts a Common Table Expression (CTE) block in SQL.

2fill in blank

medium

Complete the code to separate two CTEs in one query.

PostgreSQL

WITH first_cte AS (SELECT id FROM users), [1] AS (SELECT id FROM orders)

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

AJOIN

BSELECT

Csecond_cte

DFROM

Attempts:

3 left

💡 Hint

Common Mistakes

Using SQL keywords like SELECT or JOIN as CTE names.

Leaving the blank empty.

Each CTE needs a unique name. Here, second_cte names the second CTE.

3fill in blank

hard

Fix the error in the CTE syntax by filling the blank.

PostgreSQL

WITH cte1 AS (SELECT * FROM table1) [1] cte2 AS (SELECT * FROM table2) SELECT * FROM cte1 JOIN cte2 ON cte1.id = cte2.id;

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

A,

BWITH

CAND

DWHERE

Attempts:

3 left

💡 Hint

Common Mistakes

Repeating WITH keyword for each CTE.

Using AND or WHERE instead of comma.

Multiple CTEs are separated by commas, not repeated WITH keywords or AND.

4fill in blank

hard

Fill both blanks to complete a query with two CTEs and a final SELECT.

PostgreSQL

WITH [1] AS (SELECT name FROM customers), [2] AS (SELECT order_id FROM orders) SELECT * FROM [1] JOIN [2] ON [1].id = [2].customer_id;

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

Acust

Borders

Ccustomers

Dsales

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent names between CTEs and final SELECT.

Using unrelated names that don't match the tables.

The first CTE is named customers and the second orders. These names match the final SELECT.

5fill in blank

hard

Fill all three blanks to create two CTEs and a final SELECT joining them.

PostgreSQL

WITH [1] AS (SELECT id, name FROM employees), [2] AS (SELECT employee_id, salary FROM salaries) SELECT [3].name, [2].salary FROM [1] JOIN [2] ON [1].id = [2].employee_id;

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

Aemps

Bemployees

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names in CTEs and SELECT.

Using aliases that don't match CTE names.

The first CTE is named employees, the second employees is reused as alias for the first CTE in the SELECT. The second CTE is named employees in the options but the correct answer uses employees and employees consistently.