Quiz on SQL Correlated Subquery

What is a correlated subquery in SQL?

In a correlated subquery, which clause typically contains the subquery?

What is the main difference between a regular subquery and a correlated subquery?

What happens if a correlated subquery is placed in the WHERE clause?

Which of the following is an example of a correlated subquery?

SELECT name
FROM employees e
WHERE salary > (SELECT AVG(salary) FROM employees);

Identify the correlated subquery:

SELECT name
FROM employees e
WHERE salary > (SELECT AVG(salary) FROM employees d WHERE d.department = e.department);

Can a correlated subquery return multiple rows?

What is the purpose of a correlated subquery in SQL?

What is the performance drawback of correlated subqueries?

Which of the following queries finds employees with salaries above their department’s average?

SELECT name
FROM employees e
WHERE salary > (
SELECT AVG(salary)
FROM employees d
WHERE d.department = e.department
);

What keyword is often used with correlated subqueries for efficiency?

Which statement is TRUE about correlated subqueries?

Which SQL engine feature can help improve correlated subquery performance?

Which clause is NOT suitable for placing a correlated subquery?

What does this query do?

SELECT e.name
FROM employees e
WHERE EXISTS (
SELECT 1
FROM projects p
WHERE p.lead_id = e.id AND p.status = ‘Active’
);