# How many datasets can a single Aggregate object take input from?

The [*Aggregate Transformation*](https://documentation.astera.com/dataflows/transformations/aggregate-transformation) is a set-level transformation which means that it can only take input from a single dataset. It creates derived values from input data. So, taking input from more than one source will result in [cardinality error.](https://astera.zendesk.com/hc/en-us/articles/115000512623-Commonly-Asked-Questions-about-Cardinality-Errors)