How would you use window functions together to build a comprehensive sales analytics report showing running totals, rankings, and period over period comparisons all in a single query?

You would combine several window functions in the same SELECT statement, each with its own appropriately configured OVER clause, such as SUM for a running total, RANK for identifying top performers within each category, and LAG for calculating change from the previous period, all calculated together efficiently in a single pass over the data rather than requiring several separate queries.

SELECT SalesPersonId, SaleMonth, Amount,
  SUM(Amount) OVER (PARTITION BY SalesPersonId ORDER BY SaleMonth) AS RunningTotal,
  RANK() OVER (PARTITION BY SaleMonth ORDER BY Amount DESC) AS MonthlyRank,
  Amount - LAG(Amount) OVER (PARTITION BY SalesPersonId ORDER BY SaleMonth) AS MonthOverMonthChange
FROM Sales;