[Solved] What does the SUM() OVER() window function calculate in PostgreSQL? — Ans: A running total of values over a specified window | PostgreSQL

PostgreSQL - Window Functions in PostgreSQL

What does the SUM() OVER() window function calculate in PostgreSQL?

AThe count of non-null values in a column

BA running total of values over a specified window

CThe average of values in the entire table

DThe total sum of all rows in the table ignoring any partition

Step-by-Step Solution

Solution:

Step 1: Understand the SUM() function with OVER()
The SUM() function when used with OVER() calculates a running total or sum over a defined window of rows.
Step 2: Differentiate from aggregate SUM()
Unlike aggregate SUM(), the window function does not collapse rows but returns a sum for each row based on the window.
Final Answer:
A running total of values over a specified window -> Option B
Quick Check:
SUM() OVER() = Running Total [OK]

Quick Trick: SUM() OVER() gives running totals, not just total sum [OK]

Common Mistakes:

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What does the SUM() OVER() window function calculate in PostgreSQL?