Calculate Cumulative Sum for Each Integer in Table
Company: Coinbase
Role: Data Scientist
Category: Data Manipulation (SQL/Python)
Difficulty: Medium
Interview Round: Onsite
numbers
+-----+
| num |
+-----+
| 1 |
| 2 |
| 13 |
| 14 |
| 15 |
+-----+
##### Scenario
You have a table containing one integer per row; for each row you must output the cumulative sum of all values that are ≤ the current row’s value.
##### Question
Write SQL that returns each number and the sum of all numbers less than or equal to it.
##### Hints
Window functions such as SUM() OVER with appropriate ordering solve this in one scan.
Quick Answer: This question evaluates competency in cumulative aggregation and ordering within SQL and related data-manipulation tools, focusing on calculating running totals across rows. It is commonly asked to measure practical application skills in the Data Manipulation (SQL/Python) domain, testing query formulation, efficiency and aggregation semantics at a practical application level.