WHERE vs ON clause filtering

Query Evaluation WHERE on Right Columns Consider this query that tries to find customers with high-value orders: Let's trace through what happens step by step: Filter Placement Effects Filter in ON Clause Now the evaluation changes dramatically: Comparing the Results Choosing Right Placement When to Use WHERE vs ON Both placements have valid use cases - it depends on your intent: Real-World Example Show all customers with their recent orders (last 30 days), including customers who haven't ordered recently:

About This Interactive Section

This section is part of the Joins: Intermediate 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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