$minN (array expression)

APPLIES TO: MongoDB vCore

The $minN operator returns the n smallest values from an array. It's useful when you want to find the lowest performing items based on numerical values, such as the smallest sales figures or lowest discount percentages.

Syntax

The syntax for the $minN operator is as follows:

{
  $minN: {
    input: <array>,
    n: <number>
  }
}

Parameters

Description
input The array from which to return the n smallest values. The array should contain numerical values.
n The number of smallest values to return. Must be a positive integer.

Example

Let's understand the usage with sample json from stores dataset.

{
  "_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74",
  "name": "Proseware, Inc. | Home Entertainment Hub - East Linwoodbury",
  "sales": {
    "totalSales": 151864,
    "salesByCategory": [
      {
        "categoryName": "Sound Bars",
        "totalSales": 2120
      },
      {
        "categoryName": "Home Theater Projectors",
        "totalSales": 45004
      },
      {
        "categoryName": "Game Controllers",
        "totalSales": 43522
      },
      {
        "categoryName": "Remote Controls",
        "totalSales": 28946
      },
      {
        "categoryName": "VR Games",
        "totalSales": 32272
      }
    ]
  },
  "staff": {
    "totalStaff": {
      "fullTime": 19,
      "partTime": 20
    }
  }
}

Example 1: Get lowest two sales values

Suppose you want to find the lowest two sales values from all sales categories to identify underperforming products.

db.stores.aggregate([
  { $match: {"_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74"} },
  {
    $project: {
      name: 1,
      lowestTwoSales: {
        $minN: {
          input: "$sales.salesByCategory.totalSales",
          n: 2
        }
      }
    }
  }
])

This produces the following output:

[
  {
    _id: '40d6f4d7-50cd-4929-9a07-0a7a133c2e74',
    name: 'Proseware, Inc. | Home Entertainment Hub - East Linwoodbury',
    lowestTwoSales: [ 2120, 28946 ]
  }
]

Example 2: Find smallest discount percentages

You can also use $minN to find the smallest discount percentages from a promotion event.

db.stores.aggregate([
  { $match: {"_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74"} },
  { $unwind: "$promotionEvents" },
  { $match: {"promotionEvents.eventName": "Major Bargain Bash"} },
  {
    $project: {
      name: 1,
      eventName: "$promotionEvents.eventName",
      smallestDiscounts: {
        $minN: {
          input: "$promotionEvents.discounts.discountPercentage",
          n: 3
        }
      }
    }
  }
])

This returns the three smallest discount percentages from the "Major Bargain Bash" promotion event.

[
  {
    _id: '40d6f4d7-50cd-4929-9a07-0a7a133c2e74',
    name: 'Proseware, Inc. | Home Entertainment Hub - East Linwoodbury',
    eventName: 'Major Bargain Bash',
    smallestDiscounts: [ 7, 8, 9 ]
  }
]

Example 3: Compare staff numbers across stores

You can use $minN to analyze staffing levels by finding stores with the lowest staff counts.

db.stores.aggregate([
  {
    $project: {
      name: 1,
      staffNumbers: ["$staff.totalStaff.fullTime", "$staff.totalStaff.partTime"],
      lowestStaffCount: {
        $minN: {
          input: ["$staff.totalStaff.fullTime", "$staff.totalStaff.partTime"],
          n: 1
        }
      }
    }
  },
  { $limit: 5 }
])

This query shows the lowest staff count (either full-time or part-time) for each store, helping identify stores with minimal staffing.

[
  {
    _id: 'af9015d8-3f6b-455f-8967-a83cc22ff018',
    name: 'VanArsdel, Ltd. | Party Goods Nook - Kunzeshire',
    staffNumbers: [ 15, 1 ],
    lowestStaffCount: [ 1 ]
  },
  {
    _id: 'ed319c06-731d-45fc-8a47-b05af8637cdf',
    name: 'Relecloud | Computer Outlet - Langoshfort',
    staffNumbers: [ 10, 3 ],
    lowestStaffCount: [ 3 ]
  },
  {
    _id: '62438f5f-0c56-4a21-8c6c-6bfa479494ad',
    name: 'First Up Consultants | Plumbing Supply Shoppe - New Ubaldofort',
    staffNumbers: [ 20, 18 ],
    lowestStaffCount: [ 18 ]
  },
  {
    _id: '71c50be7-5c69-4a01-9218-e479fdeb6cee',
    name: 'Wide World Importers | Carpets Market - Port Newtonburgh',
    staffNumbers: [ 1, 14 ],
    lowestStaffCount: [ 1 ]
  },
  {
    _id: '4dc0275d-b554-4b0a-a1b2-0f14154be71d',
    name: 'VanArsdel, Ltd. | DJ Equipment Outlet - Lake Edmond',
    staffNumbers: [ 2, 13 ],
    lowestStaffCount: [ 2 ]
  }
]

Example 4: Identify underperforming categories across all stores

Find the bottom two sales values across all stores to identify consistently underperforming product categories.

db.stores.aggregate([
  { $match: { "sales.salesByCategory": { $exists: true, $ne: [] } } },
  {
    $project: {
      name: 1,
      location: 1,
      bottomTwoSales: {
        $minN: {
          input: "$sales.salesByCategory.totalSales",
          n: 2
        }
      }
    }
  },
  { $sort: { "bottomTwoSales.0": 1 } },
  { $limit: 3 }
])

This query returns the three stores with the overall lowest minimum sales values, helping identify locations that may need more support or different product strategies.

[
  {
    _id: 'c601ced7-d472-47e8-91c1-f213e3f60250',
    name: 'Tailwind Traders | Bed and Bath Bazaar - West Imaniside',
    location: { lat: -41.113, lon: -108.3752 },
    bottomTwoSales: [ 101, 12774 ]
  },
  {
    _id: '09782c05-a134-43a1-a65b-6a332bc89d7c',
    name: 'Tailwind Traders | Microphone Deals - Sonnytown',
    location: { lat: -61.9575, lon: 55.2523 },
    bottomTwoSales: [ 102, 18531 ]
  },
  {
    _id: '57303916-24f1-43a9-a50c-b96fb76ae40c',
    name: 'Fabrikam, Inc. | Art Supply Boutique - Port Geovanni',
    location: { lat: 63.9018, lon: -125.7517 },
    bottomTwoSales: [ 102, 6352 ]
  }
]

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