Running totals are crucial for tracking changes over time or across categories. Imagine analyzing sales figures; you might want to see how total sales grow each month. Or, in a logistics context, you might need to calculate the cumulative weight of packages loaded onto a truck. SQL's window functions are the key to efficiently calculating these running totals.Window functions operate on a set of rows related to the current row, without grouping the data. This is different from aggregate functions like SUM, which group data into summary rows. The `SUM()` function, when used with a `PARTITION BY` clause, can be part of a running total calculation, but it doesn't inherently provide the cumulative effect.The `SUM() OVER()` window function is the most common way to calculate running totals. The `OVER()` clause specifies the window of rows to consider when calculating the sum. Different window frame specifications allow for various running total calculations, such as cumulative sums, running averages, and more.