📊 GROUP BY – Grouping Data and Performing Aggregate Functions

(because sometimes you want to calculate things on grouped data, not individual rows)

🔧 Quick Syntax

SELECT column, aggregate_function(column)
FROM table
GROUP BY column;

This tells SQL:
“Group the rows by a column, and apply aggregate functions (like SUM, AVG, COUNT) on the grouped data.”

👀 Imagine You Have This Table:

🧑 sales table:

Scenario: You want to calculate the total quantity sold for each product.

Step 1: GROUP BY Product

Here, we’ll group by the product to calculate the total quantity sold for each one.

SELECT product, SUM(quantity) AS total_quantity
FROM sales
GROUP BY product;

✅ Result:

🧃 Recap

• GROUP BY groups the data by a column (in this case, product).
• We use aggregate functions like SUM, AVG, COUNT on the grouped data.
• The result shows total quantities sold for each product.