[Solved] Why does SUM(amount) OVER () return the same value for every row in the result set? — Ans: Because it calculates the total sum over all rows without partitioning | SQL

SQL - Advanced Window Functions

Why does SUM(amount) OVER () return the same value for every row in the result set?

ABecause it sums only the current row's amount

BBecause it calculates the total sum over all rows without partitioning

CBecause it groups rows by amount before summing

DBecause it orders rows and sums cumulatively

Step-by-Step Solution

Solution:

Step 1: Understand window function without partition
Without PARTITION BY, the window function considers all rows as one group.
Step 2: Explain why sum is same for all rows
SUM(amount) OVER () sums all rows and returns that total for each row.
Final Answer:
It calculates the total sum over all rows without partitioning -> Option B
Quick Check:
Empty OVER() means full table aggregation [OK]

Quick Trick: Empty OVER() means sum over entire table [OK]

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Why does SUM(amount) OVER () return the same value for every row in the result set?