Yes, now it's possible to do joint like searches, i.e. a second search is done on the results of the first search.
More explanation on the global MRQL page.
mrql: category=REQ and label=adult ==> category=TC and uplinkm=previous
The keyword previous refers to the set of results from the 1st part of the query
The ==> sign can also be the keyword THEN.
You can add many levels:
mrql: category=REQ and label=adult ==> category=SPEC and uplinkm=previous and label=internal ==> category=XTC and testResult=error
This would list the failed tests who has a SPEC with a label "internal" as ancestor, but only if these SPECs have a REQ with a label "adult"
The relations that can be used with previous are: