Hello, Data! Meet SQL

Beyond files and APIs, data is often stored in relational databases—systems designed for efficient, structured storage and retrieval. Relational databases store data in tables, like a spreadsheet, with rows and columns. But unlike a single file, databases can connect multiple tables, enforce data consistency, and efficiently handle huge volumes of records.

To interact with and fetch data from these databases, we use Structured Query Language (SQL), the primary tool for interacting with relational databases. At its core, SQL lets us select the information we need, specify where it comes from, and narrow down results to exactly what’s relevant.

In this lesson, we’ll explore the fundamental building blocks of SQL queries—how to select data, apply filters, and return only what’s relevant.

Sample data: Employees table

Let’s start with a simple example table called employees to understand how SQL works. It stores information about employees in a company, including their ID, name, department, hire date, and salary.