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$top

The `$top` operator sorts documents on one or more fields specified by the query and returns the first document matching the filtering criteria. It combines sorting and selection in a single operation.

Syntax

{
  $top: {
    output: [listOfFields],
    sortBy: {
      <fieldName>: <sortOrder>
    }
  }
}

Parameters

listOfFieldsobjectrequired

The list of fields to be returned for the first document in the result set.

fieldNamestringrequired

The field to use for sorting the result set.

sortOrdernumberrequired

1 or -1. 1 implies ascending order while -1 implies descending order.

Examples

Sample Data

{
  "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
  "name": "First Up Consultants | Beverage Shop",
  "sales": {
    "totalSales": 75670
  },
  "promotionEvents": [
    {
      "eventName": "Unbeatable Bargain Bash",
      "discounts": [
        { "categoryName": "Whiskey", "discountPercentage": 7 }
      ]
    }
  ]
}

Get the top selling category per store

Find the highest-selling category within a company using $top.

This query sorts documents by total sales and returns the top document per company.

Query:

db.stores.aggregate([
  {
    $match: { company: { $in: ["First Up Consultants"] } }
  },
  {
    $group: {
      _id: "$company",
      topSales: {
        $top: {
          output: ["$company", "$sales"],
          sortBy: { "sales.totalSales": -1 }
        }
      }
    }
  }
])

Output:

[
  {
    "_id": "First Up Consultants",
    "topSales": [
      "First Up Consultants",
      {
        "salesByCategory": [
          { "categoryName": "Towel Sets", "totalSales": 520 },
          { "categoryName": "Bath Accessories", "totalSales": 41710 }
        ],
        "revenue": 279183
      }
    ]
  }
]

Get the highest discount by promotion category

Fetch the highest discount per sales category across all promotions.

This query unwinds promotion events and finds the maximum discount per category.

Query:

db.stores.aggregate([
  { $unwind: "$promotionEvents" },
  { $unwind: "$promotionEvents.discounts" },
  {
    $group: {
      _id: "$_id",
      storeName: { $first: "$name" },
      highestDiscount: {
        $top: {
          sortBy: {
            "promotionEvents.discounts.discountPercentage": -1
          },
          output: {
            categoryName: "$promotionEvents.discounts.categoryName",
            discountPercentage: "$promotionEvents.discounts.discountPercentage"
          }
        }
      }
    }
  }
])

Output:

[
  {
    "_id": "64ec6589-068a-44a6-be5b-9d37bb0a90f1",
    "storeName": "First Up Consultants | Computer Gallery",
    "highestDiscount": {
      "categoryName": "Gaming Accessories",
      "discountPercentage": 24
    }
  }
]

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