$trunc

  • 04/11/2025

The $trunc operator is used to truncate a number to a specified decimal place. This operator is particularly useful in scenarios where you need to limit the precision of numerical data, such as financial calculations, reporting, or data normalization.

Syntax

{ $trunc: [ <number>, <place> ] }

Parameters

Parameter Description
<number> The number to truncate.
<place> The decimal place to truncate to. A positive value truncates to the right of the decimal point, and a negative value truncates to the left of the decimal point.

Example(s)

Truncate Latitude

This example demonstrates how to use the $trunc operator to truncate the latitude value in the location field to 2 decimal places.

db.collection.aggregate([
  {
    $project: {
      truncatedLat: { $trunc: ["$location.lat", 2] }
    }
  }
])

This truncates the lat value to two decimal places:

[
  { "_id": 1, "location": { "lat": 37.774929 }, "truncatedLat": 37.77 },
  { "_id": 2, "location": { "lat": 40.712776 }, "truncatedLat": 40.71 }
]

Truncate Sales

In this example, we truncate the fullSales value in the sales field to the nearest integer.

db.collection.aggregate([
  {
    $project: {
      truncatedSales: { $trunc: ["$sales.fullSales", 0] }
    }
  }
])

This truncates fullSales to the nearest whole number by removing the decimal portion:

[
  { "_id": 3, "sales": { "fullSales": 1234.56 }, "truncatedSales": 1234 },
  { "_id": 4, "sales": { "fullSales": 9876.99 }, "truncatedSales": 9876 }
]

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