SQL Essential Refresher

When working in a fast-paced retail environment, analysts often need to answer quick questions like “Which VIP customers placed orders last week?” “Which products have the lowest stock?” or “Which suppliers consistently deliver on time?”

These everyday questions require analysts to write precise SQL queries efficiently.

That is why it is essential to keep SQL foundations sharp and understand not just how to write queries but also how they are structured and executed behind the scenes. This lesson will review the most important SQL essentials to ensure we can confidently build and read queries in upcoming pattern-based lessons.

By the end of this lesson, we’ll be able to:

• Use SELECT, FROM, WHERE, and ORDER BY effectively.

• Write meaningful joins and subqueries.

• Understand how SQL queries execute step by step.

• Apply SQL best practices for readability and performance.

Let’s jump into the building blocks of SQL with clear explanations and examples from our course database.

SELECT, FROM, WHERE: The core of every query

These three clauses form the core of nearly every SQL query. It’s important to understand their purpose and order ...