Window Functions

ROWNUMBER, RANK, DENSERANK, LAG, LEAD, running totals — powerful analytics without losing row detail. ## Lesson objectives In this lesson, we will learn in SQL. In previous lessons, we learned how to use to group data. gives summary results by group: for example, employee count by department, average salary by department, total sales by product, and so on. But when we use , individual rows disappear. The result becomes group-level. Sometimes we want to keep individual rows and also show summary calculations next to those rows.