At Westonci.ca, we provide clear, reliable answers to all your questions. Join our vibrant community and get the solutions you need. Get quick and reliable solutions to your questions from a community of experienced professionals on our platform. Connect with a community of professionals ready to help you find accurate solutions to your questions quickly and efficiently.

Why is it necessary for each "group by" expression in SQL to include at least one column that is not an outer reference? Explain the significance of this requirement in the context of SQL queries and data aggregation.