What is the purpose of using a group by clause in a query?

The use of a group by clause in a query is primarily to compute aggregated results based on specified categories. When data needs to be summarized, such as calculating totals, averages, or counts for distinct groups within a dataset, the group by clause allows the user to categorize rows sharing common values in specified columns. This means that aggregation functions like COUNT, SUM, AVG, MAX, or MIN can be applied to derive summarized information from the grouped data.

For example, if you have a dataset of sales records and you want to find the total sales amount for each product category, you would group your query by the product category and apply an aggregation function to get the total sales per category. This functionality is essential for producing meaningful insights from large datasets where details need to be consolidated into broader trends and patterns.