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Introduction to Modern Databases

Aggregate Functions and Grouping

Explore how to apply SQL aggregate functions like COUNT, SUM, AVG, MIN, and MAX to analyze data effectively. Understand grouping data with GROUP BY and filtering grouped results using HAVING to create insightful reports. This lesson equips you with essential skills to summarize large datasets and perform segmented data analysis for better decision-making.

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Imagine you’re managing an OnlineStore, and your manager asks questions like:

  • What was our total revenue last month?

  • Which product category is the most popular?

Simply scanning through individual rows in the Orders or Products tables won’t give us those answers. To uncover these insights, we need a way to summarize or aggregate our data—turning raw records into meaningful information that supports better decisions.

By the end of this lesson, we will learn to:

  • Understand and use common aggregate functions like COUNT(), SUM(), AVG(), MIN(), and MAX().

  • Group data into meaningful segments using the GROUP BY clause.

  • Filter these groups based on aggregated results using the HAVING clause.

Let’s get started on turning our raw data into valuable information!

Understanding aggregate functions

In database queries, we don’t always want to see a long list of individual records. More often, we need a summary. For instance, knowing the total number of customers is more useful than just listing every single customer. Aggregate functions ...