Correlated Subqueries

How can we compare each record against its own group average?

Advanced⏱ 3 Minutes⭐ 280 XP

🤔 THE QUESTION

How can we compare each record against its own group average?

💡 WHAT IS IT?

A correlated subquery references columns from the outer query, evaluating once per outer row.

🎯 WHAT IS IT USED FOR?

Finding employees earning above their own department average, top performers within branch.

💻 EXAMPLE

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

Practice typing production-grade SQL code for Correlated Subqueries.