Aggregations: Counting, Summing, and Averaging Your Data

You know the basics. SELECT, WHERE, ORDER BY, LIMIT. Now let's talk about the queries that actually answer business questions. Not "give me these rows." But "how many customers bought more than twice last month?" Or "what is the average order value per city?" Or "which product category drives the most revenue?" These questions require aggregation. Collapsing many rows into summary numbers. And SQL's aggregation tools are precise, fast, and more powerful than they first appear. The Five Core Aggr