Querying Databases with SQL

In this chapter, you’ll learn the essential aspects of databases, starting with a broad overview, then diving deep into the fundamental language of SQL, exploring crucial concepts such as subqueries, JOIN, CASE WHEN, window functions, aggregations, and how to tackle complex queries.

Our goal is to provide you with the knowledge and tools necessary to tackle any database-related question in a technical interview effectively. This is crucial for those preparing for a technical interview because understanding databases is a foundational skill for data scientists; equipped with the knowledge shared in these chapters, you’ll be ready to face any database question confidently and proficiently.

So, in this chapter, we will cover the following topics:

• Introducing relational databases
• Mastering SQL basics
• Aggregating with GROUP BY and HAVING
• Creating fields with CASE WHEN
• Analyzing subqueries and CTEs
• Merging tables...