01. Video: Introduction

What this lesson is about…

Up to this point you have learned a lot about working with data using SQL. This lesson will focus on three topics:

1. Subqueries
2. Table Expressions
3. Persistent Derived Tables

Both subqueries and table expressions are methods for being able to write a query that creates a table, and then write a query that interacts with this newly created table. Sometimes the question you are trying to answer doesn't have an answer when working directly with existing tables in database.

However, if we were able to create new tables from the existing tables, we know we could query these new tables to answer our question. This is where the queries of this lesson come to the rescue.

If you can't yet think of a question that might require such a query, don't worry because you are about to see a whole bunch of them!