Database
[{"Geography":{"Tourism":{"B001":{"code":"B001","max":" 140","min":" 97","minWithQuota":" 91"}}},"MathAndPhysic":{"IT":{"B183":{"code":"B183","max":"140","min":" 50","minWithQuota":"none","quotes":[]}}}}]
Query
db.collection.find({"MathAndPhysic.IT.B183":{$exists:true}},{"B183":"$MathAndPhysic.IT.B183"})