You can only retrieve an object or a list of objects. You can not retrieve a combination of objects of different entities in a single retrieve.
What do you want to do?
A database retrieve can be modeled in Studio as follows:
if you are a developer and want to do more awesome stuff; install Studio pro.
This editor allows for more advanced modeling.
Also take a look at these learning paths:
XPath module: https://gettingstarted.mendixcloud.com/link/module/22/lecture/122
Can i install studiopro in mac os.I am not able to install studiopro in mac os.Is there any possibility please let me know.