$min (field update operator)

APPLIES TO: MongoDB vCore

The $min operator updates the value of a field to a specified value if the specified value is less than the current value of the field. If the field does not exist, $min creates the field and sets it to the specified value. This operator is useful for maintaining minimum thresholds or tracking the lowest values.

Syntax

The syntax for the $min operator is as follows:

{
  $min: {
    <field1>: <value1>,
    <field2>: <value2>,
    ...
  }
}

Parameters

Description
field The name of the field to update with the minimum value.
value The value to compare with the current field value. The field will be updated only if this value is smaller.

Example

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

{
  "_id": "26afb024-53c7-4e94-988c-5eede72277d5",
  "name": "First Up Consultants | Microphone Bazaar - South Lexusland",
  "staff": {
    "totalStaff": {
      "fullTime": 14,
      "partTime": 8
    }
  },
  "sales": {
    "totalSales": 83865,
    "salesByCategory": [
      {
        "categoryName": "Lavalier Microphones",
        "totalSales": 44174
      },
      {
        "categoryName": "Wireless Microphones",
        "totalSales": 39691
      }
    ]
  }
}

Example 1: Setting minimum staff requirements

Set a minimum staff requirement, updating only if the current value is higher.

db.stores.updateOne(
  { "_id": "26afb024-53c7-4e94-988c-5eede72277d5" },
  {
    $min: {
      "staff.totalStaff.fullTime": 10
    }
  }
)

Since the current fullTime value is 14, and 10 is less than 14, the field will be updated to 10.

Example 2: Multiple field updates

Update multiple fields with minimum values simultaneously.

db.stores.updateOne(
  { "_id": "26afb024-53c7-4e94-988c-5eede72277d5" },
  {
    $min: {
      "staff.totalStaff.partTime": 12,
      "sales.totalSales": 50000
    }
  }
)

In this case:

  • partTime (8) will be updated to 8 since 12 > 8 (no change)
  • totalSales (83865) will be updated to 50000 since 50000 < 83865

Example 3: Creating new fields

If a field doesn't exist, $min creates it with the specified value.

db.stores.updateOne(
  { "_id": "26afb024-53c7-4e94-988c-5eede72277d5" },
  {
    $min: {
      "staff.minStaffRequired": 15,
      "sales.minimumSalesTarget": 30000
    }
  }
)

Example 4: Working with Dates

Set minimum dates for tracking earliest events.

db.stores.updateOne(
  { "_id": "26afb024-53c7-4e94-988c-5eede72277d5" },
  {
    $min: {
      "lastInventoryCheck": new Date("2024-01-15"),
      "firstSaleDate": new Date("2023-06-01")
    }
  }
)

Example 5: Updating array elements

Update minimum values within array elements using positional operators.

db.stores.updateOne(
  {
    "_id": "26afb024-53c7-4e94-988c-5eede72277d5",
    "sales.salesByCategory.categoryName": "Lavalier Microphones"
  },
  {
    $min: {
      "sales.salesByCategory.$.totalSales": 40000
    }
  }
)

After these operations, the document would be updated as follows:

{
  "_id": "26afb024-53c7-4e94-988c-5eede72277d5",
  "name": "First Up Consultants | Microphone Bazaar - South Lexusland",
  "staff": {
    "totalStaff": {
      "fullTime": 10,
      "partTime": 8
    },
    "minStaffRequired": 15
  },
  "sales": {
    "totalSales": 50000,
    "minimumSalesTarget": 30000,
    "salesByCategory": [
      {
        "categoryName": "Lavalier Microphones",
        "totalSales": 40000
      },
      {
        "categoryName": "Wireless Microphones",
        "totalSales": 39691
      }
    ]
  },
  "lastInventoryCheck": ISODate("2024-01-15T00:00:00.000Z"),
  "firstSaleDate": ISODate("2023-06-01T00:00:00.000Z")
}

Related content