joins2

db.homeSales.aggregate([
  {$match: {
    amount: {$gte:3000000}}
  }, 
  {$lookup: {
    from: "postcodes", 
    localField: "address.postcode",
    foreignField: "postcode",
    as: "postcode_docs"}
  },
  {$project: {
    _id: 0,
    saleDate: "$date",
    price: "$amount",
    address: 1,
    location: "$postcode_docs.location"}},
  {$sort:
    {
      price: -1
    }}
])