In SQL, aggregate functions are used to perform calculations on a set of values and return a single value as the result. The GROUP BY clause is used in combination with aggregate functions to group rows based on one or more columns.

Let’s say we have a table called orders with the following columns: order_id, customer_id, product_id, and order_amount. We want to calculate the total order amount for each customer.

Here’s an example query that uses the SUM aggregate function with GROUP BY:

SELECT customer_id, SUM(order_amount) AS total_order_amount
FROM orders
GROUP BY customer_id;

In this query:

• We select the customer_id column and calculate the sum of order_amount for each customer.
• The result is aliased as total_order_amount using the AS keyword.
• The GROUP BY clause groups the rows by the customer_id column.

The output of this query will be a result set with two columns: customer_id and total_order_amount. Each row represents a unique customer and the total order amount for that customer.

You can also use other aggregate functions like COUNT, AVG, MIN, MAX, etc., along with GROUP BY to perform different calculations on grouped data.

Note: The columns that are not part of the GROUP BY clause should be used with an aggregate function or included in the SELECT clause as part of the grouping.

#SQL #AggregateFunctions