Mastering Advanced SQL: Beyond the Basics

If you’ve grasped the fundamentals of SQL and are ready to take your skills to the next level, this guide is for you. Advanced SQL techniques allow you to write more efficient, powerful, and complex queries, enabling you to unlock deeper insights from your data. Here, we’ll explore several advanced SQL concepts and provide examples to help you master them.

Advanced SQL Topics

1. Subqueries and Nested Queries

Subqueries, or inner queries, are queries within a query. They can be used to perform complex operations, such as filtering data based on the results of another query.

Example:

-- Find the names of employees who earn more than the average salary
SELECT name 
FROM employees 
WHERE salary > (SELECT AVG(salary) FROM employees);

2. Common Table Expressions (CTEs)

CTEs are temporary result sets that can be referenced within a SELECT, INSERT, UPDATE, or DELETE statement. They improve the readability and organization of complex queries.

Example:

WITH SalesCTE AS (
    SELECT employee_id, SUM(sales) AS total_sales
    FROM sales
    GROUP BY employee_id
)
SELECT employee_id, total_sales
FROM SalesCTE
WHERE…