SQL Running Total Explained: SUM() OVER PARTITION BY | Advanced SQL Window Function Tutorial

Published: 11 July 2026
on channel: DataEngineers Academy

Welcome to *Data Engineers Academy**! In this advanced SQL tutorial, we will learn how to calculate a **Running Total using SUM() OVER PARTITION BY* and understand one of the most important SQL window function techniques.

Running totals are widely used in real-world data analytics, reporting, finance, sales analysis, and data engineering workflows. The SUM() OVER() window function allows you to calculate cumulative values while keeping individual rows visible.

In this video, you will learn:

How to calculate running totals in SQL
How the SUM() OVER() window function works
How to use PARTITION BY for grouped running totals
How ORDER BY controls cumulative calculations
How to analyze time-series and transactional data
How to solve SQL interview questions using window functions

SQL Concepts Covered:

✅ SUM() Window Function
✅ OVER() Clause
✅ PARTITION BY
✅ ORDER BY in Window Functions
✅ Running Total Calculation
✅ Cumulative Sum Analysis
✅ Advanced SQL Window Functions

Problem Overview:

A running total shows the cumulative value of a metric over time. Businesses use running totals to track:

Cumulative sales growth
Account balances
Monthly revenue trends
Customer spending patterns
Inventory movement
Performance metrics

Using SUM() OVER PARTITION BY provides an efficient way to calculate these values without complex self-joins or subqueries.

What You Will Learn:

Difference between normal SUM() and window SUM()
How PARTITION BY creates separate running totals
How to calculate cumulative values by customer, category, or department
How to write clean and optimized SQL queries
How running totals are used in real-world analytics
How to answer SQL interview questions confidently

Real-World Applications:

Running totals are commonly used in:

Data warehouse reporting
Business dashboards
Financial analysis
Customer analytics
ETL and ELT pipelines
Performance tracking systems

Who Should Watch This Video?

This tutorial is useful for:

📌 Data Engineers preparing for SQL interviews
📌 Data Analysts working with reports
📌 SQL Developers improving query skills
📌 Database Professionals
📌 Anyone learning advanced SQL analytics

Interview Preparation Topics:

SQL Window Function Interview Questions
Running Total SQL Problems
SUM OVER PARTITION BY Examples
Cumulative Sum SQL Queries
Advanced SQL Coding Challenges
Real-World Data Analysis Problems

Mastering window functions like SUM() OVER PARTITION BY is essential for writing powerful SQL queries and solving advanced data problems.

Follow *Data Engineers Academy* for more SQL tutorials, interview questions, and practical data engineering challenges.

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