List Distinct Field Values

You can list the distinct values of a document field in a collection by calling the distinct() method on a Collection instance. For example, if documents in a collection contain the date field, you can use the distinct() method to find all the possible values for that field in the collection.

Pass a field name as a parameter to the distinct() method to return the distinct values for that field. You can also pass a query filter as a parameter to find distinct field values from only a subset of matched documents. To learn more about creating query filters, see the Specify a Query guide.

The distinct() method returns the list of distinct values as a Vec<Bson> type, a vector of Bson values.

Example

This example finds distinct values for a field in the restaurants collection of the sample_restaurants database.

This example finds distinct values of the borough field in the subset of documents in which the value of the cuisine field is "Turkish".

Select the Asynchronous or Synchronous tab to see the corresponding code for each runtime:

use std::env;
use mongodb::{ 
    bson::{ Document, doc },
    Client,
    Collection };
#[tokio::main]
async fn main() -> mongodb::error::Result<()> {
    let uri = "<connection string>";
    let client = Client::with_uri_str(uri).await?;
    let my_coll: Collection<Document> = client
        .database("sample_restaurants")
        .collection("restaurants");
    let filter = doc! { "cuisine": "Turkish" };
    let boroughs = my_coll.distinct("borough", filter).await?;
    println!("List of field values for 'borough':");
    for b in boroughs.iter() {
        println!("{:?}", b);
    }
    Ok(())
}

List of field values for 'borough':
String("Brooklyn")
String("Manhattan")
String("Queens")
String("Staten Island")

use std::env;
use mongodb::{ 
    bson::{ Document, doc },
    sync::{ Client, Collection }
};
fn main() -> mongodb::error::Result<()> {
    let uri = "<connection string>";
    let client = Client::with_uri_str(uri)?;
    let my_coll: Collection<Document> = client
        .database("sample_restaurants")
        .collection("restaurants");
    let filter = doc! { "cuisine": "Turkish" };
    let boroughs = my_coll.distinct("borough", filter).run()?;
    println!("List of field values for 'borough':");
    for b in boroughs.iter() {
        println!("{:?}", b);
    }
    Ok(())
}

List of field values for 'borough':
String("Brooklyn")
String("Manhattan")
String("Queens")
String("Staten Island")

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