distinct

  • 11/08/2024

APPLIES TO: MongoDB vCore

The distinct command is used to find the unique values for a specified field across a single collection. This command is useful when you need to identify the set of distinct values for a field without retrieving all the documents or when you need to perform operations like filtering or grouping based on unique values.

Syntax

The basic syntax of the distinct command is as follows:

db.collection.distinct(field, query, options)
  • field: The field that receives the returned distinct values.
  • query: Optional. A query that specifies the documents from which to retrieve the distinct values.
  • options: Optional. Other options for the command.

Examples

Here are examples using the provided sample JSON structure.

Example 1: Find distinct categories in sales

To find the distinct categoryName in the salesByCategory array:

db.stores.distinct("sales.salesByCategory.categoryName")

Sample output

[mongos] StoreData> db.stores.distinct("sales.salesByCategory.categoryName")
[
  {
    _id: 'Discount Derby',
    discounts: [
      { categoryName: 'Bath Sheets', discountPercentage: 25 },
      { categoryName: 'Tablecloths', discountPercentage: 25 },
      { categoryName: 'Drapes', discountPercentage: 25 }
    ]
  }
]
[mongos] StoreData> db.stores.distinct("sales.salesByCategory.categoryName")
[
  'Music Theory Books',
  'Superfoods',
  'Harmonicas',
  'Garden Tools',
  ... 883 more items
]

Example 2: Find distinct event names in promotion events

To find the distinct eventName in the promotionEvents array:

db.stores.distinct("promotionEvents.eventName")

Sample output

[mongos] StoreData> db.stores.distinct("promotionEvents.eventName")
[
{
    _id: 'Super Saver Celebration',
    discounts: [
      { categoryName: 'Face Towels', discountPercentage: 25 },
      { categoryName: 'Printer Ribbons', discountPercentage: 25 },
      { categoryName: 'Chromebooks', discountPercentage: 25 }
    ]
    }
]

Example 3: Find distinct discount percentages for a specific event

To find the distinct discountPercentage in the discounts array for the "Summer Sale" event:

db.stores.distinct("promotionEvents.discounts.discountPercentage", { "promotionEvents.eventName": "Incredible Discount Days" })

Sample output

[mongos] StoreData> db.stores.distinct("promotionEvents.discounts.discountPercentage", { "promotionEvents.eventName": "Incredible Discount Days" })
[
   6, 17, 22, 25,  9, 15, 14,
   7, 12, 19, 24,  5, 20, 10,
  23, 16, 18, 21, 13, 11,  8
]

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