How does the GROUP BY clause work in SQL?

Can you explain how the GROUP BY clause works in SQL?

Sure! The GROUP BY clause is used to arrange identical data into groups. It is often used with aggregate functions like COUNT, SUM, AVG, etc.

Can you give me an example of how to use GROUP BY?

Of course! For instance, if you have a table of sales data, you can group by the 'product_id' to see total sales for each product using: SELECT product_id, SUM(sales) FROM sales_table GROUP BY product_id;

What happens if I don't include an aggregate function with GROUP BY?

If you don't include an aggregate function, SQL will return an error because it won't know how to summarize the grouped data.

Can I use multiple columns in the GROUP BY clause?

Yes, you can! Just separate the columns with commas. For example: GROUP BY column1, column2.