How to add COUNT/SUM/AVG fields inside a datasource inside a Data Entity in AX 7 (Dynamics 365 for operation)

Hello all,

In Dynamics AX 2012 R3, we used to create a query and add a datasource under it, and within that datasource we used to insert a new field based on COUNT/AVG/SUM etc.

How can we add these same types of COUNT/AVG/SUM fields within a data source inside a data entity in Dynamics 365 for Operations (AX 7)??

Can anyone guide me in this?