Subqueries & Nested Queries - Concepts
Explore the key concepts of subqueries & nested queries with practical examples and exercises.
45 min•By Priygop Team•Last updated: Feb 2026
Introduction to Subqueries & Nested Queries
In this section, we cover the fundamental aspects of subqueries & nested queries. You'll learn core concepts, see real-world examples, and understand how to apply them in your projects.
Key Concepts
- Understanding the core principles of subqueries & nested queries
- Practical applications and real-world use cases
- Step-by-step implementation guides
- Common patterns and best practices
- Tips for debugging and troubleshooting
- Performance optimization techniques
Subqueries & Nested Queries - Code Example
Example
-- Subquery in WHERE
SELECT name, salary
FROM employees
WHERE salary > (SELECT AVG(salary) FROM employees);
-- Subquery in FROM (derived table)
SELECT dept, avg_sal
FROM (
SELECT department AS dept, AVG(salary) AS avg_sal
FROM employees
GROUP BY department
) AS dept_stats
WHERE avg_sal > 60000;
-- EXISTS subquery
SELECT c.name
FROM customers c
WHERE EXISTS (
SELECT 1 FROM orders o
WHERE o.customer_id = c.id
AND o.total > 1000
);Try It Yourself: Subqueries & Nested Queries
Try It Yourself: Subqueries & Nested QueriesJavaScript⚠ 1 error
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