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$max

The `$max` operator returns the maximum value of a set of input values. It can be used as an accumulator operator in aggregation or as a field update operator to set a field to a value only if the new value is greater than the current value.

Syntax

$max: <expression>

Parameters

expressionobjectrequired

Any valid expression that resolves to a value. The $max operator evaluates this expression to determine the maximum value.

Examples

Sample Data

{
  "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
  "name": "First Up Consultants | Beverage Shop",
  "sales": {
    "totalSales": 75670,
    "salesByCategory": [
      { "categoryName": "Wine Accessories", "totalSales": 34440 }
    ]
  }
}

Calculate the highest sales by category

Calculate the highest sales within each category across all stores.

This query groups documents by sales category and returns the maximum sales per category.

Query:

db.stores.aggregate([
  { $unwind: "$sales.salesByCategory" },
  {
    $group: {
      _id: "$sales.salesByCategory.categoryName",
      maxSales: {
        $max: "$sales.salesByCategory.totalSales"
      }
    }
  }
])

Output:

[
  { "_id": "Christmas Trees", "maxSales": 49697 },
  { "_id": "Nuts", "maxSales": 48020 },
  { "_id": "Camping Tables", "maxSales": 48568 },
  { "_id": "Music Theory Books", "maxSales": 46133 },
  { "_id": "Fortified Wine", "maxSales": 49912 }
]

Using $max in $bucket

Retrieve the highest sales within buckets of sales boundaries.

This query creates sales buckets and finds the maximum sales in each bucket.

Query:

db.stores.aggregate([
  {
    $bucket: {
      groupBy: "$sales.totalSales",
      boundaries: [0, 1000, 5000, 10000],
      default: "Other",
      output: {
        maxSales: { $max: "$sales.totalSales" }
      }
    }
  }
])

Output:

[
  { "_id": 1000, "maxSales": 4996 },
  { "_id": "Other", "maxSales": 404106 },
  { "_id": 0, "maxSales": 995 },
  { "_id": 5000, "maxSales": 9999 }
]

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