SUM() OVER

SUM() OVER is a SQL function in the Window Functions category. Windowed aggregate — calculates running totals or partitioned sums without collapsing rows. The syntax is SUM(column) OVER (PARTITION BY col ORDER BY col). It accepts column. It returns windowed aggregate. A typical example: SELECT date, revenue, SUM(revenue) OVER (ORDER BY date) AS running_total FROM daily_sales; -- Running cumulative total over time SELECT dept, name, salary, SUM(salary) OVER (PARTITION BY dept) AS dept_total FROM employees; -- Total salary per department A close relative is ROW_NUMBER(), which assigns a unique sequential integer to each row within its partition (1, 2, 3...). A close relative is RANK(), which similar to ROW_NUMBER but gives the same rank to equal values. Leaves gaps in ranking. A close relative is DENSE_RANK(), which like RANK but without gaps. Equal values get the same rank, and the next number follows sequentially. More about this category: Window/analytical functions — ROW_NUMBER, RANK, DENSE_RANK, LAG, LEAD, NTILE.