What is a 'Window Function' in SQL?

What is a 'Window Function' in SQL?

Approach: Explain calculation across a set of table rows related to the current row.

A function that performs a calculation across a set of table rows that are somehow related to the current row. Unlike aggregate functions, it does not group rows into a single output row.

Follow-up: What is the difference between RANK and DENSE_RANK?

Key concepts: over clause, partition by, running total.