SUM and AVG calculations

Concepts covered: sqlSumAvg

SUM Functions Basic Example SUM with GROUP BY Each group's amounts are added together into a single total. North's three sales (150 + 175 + 190) become 515, while East's lone sale stays at 160. Now you can instantly see which region generates the most revenue and sells the most units. SUM with Expressions You can sum calculated values, not just raw columns. This is common for computing totals from unit prices and quantities. The expression price * quantity is calculated for each row, then those products are summed together. Grand vs Group Totals Handling Empty Data Database Execution AVG Functions AVG() Basic Example The average order value across all orders is $127.43. AVG with GROUP BY Each group's salaries are averaged independently. Engineering's three salaries produce a higher mean th

About This Interactive Section

This section is part of the Aggregating: 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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