Absolute Free C100DEV Exam Practice for Comprehensive Preparation 

db.orders.aggregate([
   {
      $group: {
         _id: "$customer_name",
         total_sales: { $sum: { $multiply: ["$items.quantity", "$items.price"] } }
      }
   }
])

db.orders.aggregate([
   {
      $unwind: "$items"
   },
   {
      $group: {
         _id: "$customer_name",
         total_sales: { $sum: { $multiply: ["$items.quantity", "$items.price"] } }
      }
   }
])

db.orders.aggregate([
   {
      $unwind: "$items"
   },
   {
      $group: {
         total_sales: { $sum: { $multiply: ["$items.quantity", "$items.price"] } }
      }
   }
])

db.orders.aggregate([
   {
      $unwind: "$items"
   },
   {
      $group: {
         _id: "$customer_name",
         total_sales: { $sum: { $multiply: ["quantity", "price"] } }
      }
   }
])

db.orders.findAndModify(
  { status: "Pending" },
  { $set: { status: "Completed" } }
)

db.orders.findAndModify({
  query: { status: "Pending" },
  update: { $set: { status: "Completed" } }
})

db.orders.findAndModify({ query: { status: "Pending" }, status: "Completed" })

db.orders.findAndModify({ status: "Pending" }, { status: "Completed" })