What does the HAVING clause do in SQL queries?

The HAVING clause in SQL is specifically designed to filter the results of a query after the data has been aggregated. When using aggregate functions such as SUM, COUNT, AVG, etc., the HAVING clause allows you to impose conditions on the aggregated results, making it an essential tool when working with grouped data.

For instance, if you aggregate sales data to find the total sales per region, you might want to limit the results to only those regions that have total sales exceeding a certain threshold. In this case, the HAVING clause would be used to specify this condition, thereby refining the output after the aggregation has been completed.

It's important to recognize that the HAVING clause operates on the result set generated by the GROUP BY clause. In contrast, filtering using the WHERE clause happens before any aggregation takes place, thus maintaining a distinct purpose between the two. This differentiates the function and utility of HAVING in SQL queries effectively, emphasizing its role in filtering aggregated data.