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Retrieve Distinct Values of a Field

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Note

If you specify a callback method, distinct() returns nothing. If you do not specify one, this method returns a Promise that resolves to the result object when it completes. See our guide on Promises and Callbacks for more information, or the API documentation for information on the result object.

You can retrieve a list of distinct values for a field across a collection by using the collection.distinct() method. Call the distinct() method on a Collection object with a document field name parameter as a String to produce a list that contains one of each of the different values found in the specified document field as shown below:

const distinctValues = collection.distinct("countries", query);

You can specify a document field within an embedded document using dot notation. If you call distinct() on an document field that contains an array, the method treats each element as a separate value. See the following example of a method call to the wins field in the awards subdocument:

const distinctValues = collection.distinct("awards.wins", query);

You can specify additional query options using the options object passed as the third parameter to the distinct() method. For details on the query parameters, see the distinct() method in the API documentation.

If you specify a value for the document field name that is not of type String such as a Document, Array, Number, or null, the method does not execute and returns a TypeMismatch error with a message that resembles the following:

"key" had the wrong type. Expected string, found <non-string type>

Visit Retrieve Distinct Values for more information about the distinct() method.

Example

The following snippet retrieves a list of distinct values for the year document field from the movies collection. It uses a query document to match movies that include "Barbara Streisand" as a director.

Note

This example connects to an instance of MongoDB and uses a sample data database. To learn more about connecting to your MongoDB instance and loading this database, see the Usage Examples guide.

1 const { MongoClient } = require("mongodb");
2 
3 // Replace the uri string with your MongoDB deployment's connection string.
4 const uri =
5   "mongodb+srv://<user>:<password>@<cluster-url>?writeConcern=majority";
6 
7 const client = new MongoClient(uri, {
8   useNewUrlParser: true,
9   useUnifiedTopology: true,
10 });
11 
12 async function run() {
13   try {
14     await client.connect();
15 
16     // define a database and collection on which to run the method
17     const database = client.db("sample_mflix");
18     const movies = database.collection("movies");
19 
20     // specify the document field
21     const fieldName = "year";
22 
23     // specify an optional query document
24     const query = { directors: "Barbra Streisand" };
25 
26     const distinctValues = await movies.distinct(fieldName, query);
27 
28     console.log(distinctValues);
29   } finally {
30     await client.close();
31   }
32 }
33 run().catch(console.dir);

← Count Documents Run a Command →

1	const { MongoClient } = require("mongodb");
2
3	// Replace the uri string with your MongoDB deployment's connection string.
4	const uri =
5	"mongodb+srv://<user>:<password>@<cluster-url>?writeConcern=majority";
6
7	const client = new MongoClient(uri, {
8	useNewUrlParser: true,
9	useUnifiedTopology: true,
10	});
11
12	async function run() {
13	try {
14	await client.connect();
15
16	// define a database and collection on which to run the method
17	const database = client.db("sample_mflix");
18	const movies = database.collection("movies");
19
20	// specify the document field
21	const fieldName = "year";
22
23	// specify an optional query document
24	const query = { directors: "Barbra Streisand" };
25
26	const distinctValues = await movies.distinct(fieldName, query);
27
28	console.log(distinctValues);
29	} finally {
30	await client.close();
31	}
32	}
33	run().catch(console.dir);