SQL Window Functions vs Aggregate Functions: Key Differences Explained

A technical guide published on DEV Community breaks down the core difference between aggregate and window functions in SQL for beginner and intermediate users. Aggregate functions like SUM() and COUNT() collapse multiple rows into a single result per group, changing the granularity of the data. Window functions perform the same calculations but retain every original row, attaching the result to each one instead of merging them. The distinction is illustrated using side-by-side SQL queries on a small product sales dataset, showing how OVER (PARTITION BY ...) syntax works without requiring a GROUP BY clause. The guide aims to help developers understand when to use each approach, particularly when individual row detail must be preserved alongside group-level totals.