SELECT and FROM basics

Concepts covered: sqlSelectFrom

Every SQL query follows a predictable structure that tells the database what data you want and where to find it. Building Your First Query Understanding the role of each keyword helps you construct queries that retrieve exactly the data you need. SELECT Columns FROM Arrange the Query Check Your Understanding Selecting only the columns you need, rather than all columns, reduces the amount of data the database must read and transfer, which makes queries faster on large tables.

About This Interactive Section

This section is part of the Query Structure: Beginner lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live PostgreSQL database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

How DataDriven Lessons Work

DataDriven combines four interview rounds (SQL, Python, Data Modeling, Pipeline Architecture) with adaptive difficulty and spaced repetition. Easy problems get harder as you improve. Weak concepts resurface until you master them. Your readiness score tracks progress across every topic interviewers test. Every lesson section ends with problems you solve by writing and running real code, not by picking multiple-choice answers.