WHERE clause for filtering rows

Concepts covered: sqlWhere

SQL checks each row one by one. For every row, it asks: does this row meet my condition? If yes, keep it. If no, skip it. The SQL code tells the database to scan the status column for each device. When status equals "active", that row passes through to the results. All other rows are filtered out. Basic pattern: Example Here is a simple example filtering students by grade. Remember Filters are built with simple comparison operators: Which query correctly filters for active users? The Equals Operator Exact matching is the most common type of filter. The equals operator lets you find rows where a column has a specific value. Basic Syntax Example • Find a specific user by email • Get an order by order number • Show products in one category • Filter data from one region What happens when you f

About This Interactive Section

This section is part of the Filtering: 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.

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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.