What does the "GROUP BY" clause do in SQL?

The "GROUP BY" clause in SQL is essential for organizing data into summary rows based on one or more columns. When you use the "GROUP BY" clause, it allows you to aggregate data by grouping together all records that share the same value in a specified column or columns. This is particularly useful when working with aggregate functions such as COUNT, SUM, AVG, MAX, or MIN, which can provide insights into the data by producing summary statistics for each group.

For example, if you have a table of sales data, and you want to find total sales for each product, you would use the "GROUP BY" clause to combine rows that have the same product identifier. The result would show one row per product with an aggregated total of sales for each.

This capability to summarize similar data points is critical in analytics and reporting, making the "GROUP BY" clause a fundamental tool for database queries. The clarity it provides in data interpretation and the ability to perform aggregation on specific groups within the dataset make it a powerful component of SQL querying.