By Michael Nocito , data analyst · Published August 10, 2026 By the end of this page you can look at any DAX aggregation and say which of the two it needs, before you write it. You will also be able to spot the wrong one in somebody else's model, including the version that returns a number close...
Source: [Dev.to](https://dev.to/michaelnocito/sum-vs-sumx-in-dax-why-a-row-by-row-calculation-needs-an-iterator-468a)