Inequality joins with BETWEEN

Concepts covered: sqlInequalityJoin

Not all joins match on exact values. Range-based matching opens up powerful patterns for lookups, attribution, and temporal analysis. Range Matching Example Suppose you have employee metrics with salaries and a cost allocation table with budget brackets. Each bracket has a min and max income. To find each employee's tax rate, match their salary to the bracket range: Each employee's salary is matched to the bracket where it falls between min_income and max_income. This is impossible with an equality join because there's no single key to match on. BETWEEN Syntax Real-World Applications Inequality joins appear frequently in analytics for event attribution, time-window matching, and ad-hoc range lookups. Event Attribution Example Another common pattern: attributing events to time windows. Matc

About This Interactive Section

This section is part of the Joins: Advanced 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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