FetchXML
Dataverse's XML-based query language — used for views, advanced find, plug-ins, and complex analytical queries.
FetchXML is Dataverse's XML-based query language. It powers Advanced Find in the Dynamics 365 UI, stored views in Dataverse (which are FetchXML under the hood), plug-ins doing complex queries via the SDK, and Power Automate flows that use FetchXML in the "List rows" action. FetchXML is more expressive than OData for complex queries with group-by, aggregations, and nested link-entity joins; it's verbose but powerful. For modern integration work — external systems calling Dataverse over HTTP — OData is the standard choice. Both compile to the same underlying SQL, so performance is comparable. Tools like XrmToolBox's FetchXML Builder make hand-writing the XML less tedious.