MongoDB existe y no nulo
db.collection1.find({ 'fieldname1' : { $exists: true, $ne: null } });
saggiyogesh
db.collection1.find({ 'fieldname1' : { $exists: true, $ne: null } });collection.find({ arrayElementName: { $exists: true, $not: {$size: 0} } })db.collection.find({arrayElementName : {$exists:true, $size:0}})db.collection1.find({'fieldname1': {$in: [null, ""]}})