db={"A":[{_id:"1",status:"Report",type:"Academy",rating:"Excellent",ReportNo:"A1"},{_id:"2",status:"Open",type:"Academy",rating:"",ReportNo:""},{_id:"3",status:"Draft",type:"Academy",rating:"",ReportNo:""},{_id:"4",status:"Report",type:"Academy",rating:"Great",ReportNo:"A4"}],"B":[{_id:"98",status:"Archived",type:"Academy",rating:"So So",ReportNo:"X2"},{_id:"99",status:"Archived",type:"Academy",rating:"Great",ReportNo:"X1"}]}

db.A.aggregate([{"$facet":{"A":[{"$match":{status:"Report"}}],"B":[{$limit:1},{"$lookup":{"from":"B","pipeline":[],"as":"B"}},{$unwind:"$B"},{"$replaceRoot":{"newRoot":"$B"}}]}},{$project:{all:{"$setUnion":["$A","$B"]}}},{$unwind:"$all"},{"$replaceRoot":{"newRoot":"$all"}}])