Running Total of Daily Sales

Problem

Schema: Sales(sale_date DATE, amount DECIMAL). One row per day. Return sale_date, amount, and running_total — the cumulative sum of amounts from the first day through that day.

Constraints

• Dates are unique.

Approach — Core Patterns

This is a Core Patterns problem. The idea: pick the data structure best matched to the constraints and solve it in one clean pass. Work through the reference code below line by line, then re-derive it yourself in the editor — that's how the pattern sticks.

Complexity: see the walkthrough below.

Solution code

SQL

SELECT sale_date, amount,
       SUM(amount) OVER (ORDER BY sale_date
                         ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS running_total
FROM Sales
ORDER BY sale_date;

Practice it

Reading a solution isn't the same as being able to write it under pressure. Open this problem in the in-browser editor, hide the solution, and solve it from scratch — your code runs against real test cases instantly.