MongoDB – Distinct() Method

MongoDB distinct() method finds the distinct values for a given field across a single collection and returns the results in an array. It takes three parameters, first one is the field for which to return distinct values and the others are optional.

• If you are using this method in the sharded cluster, then it may return orphaned documents.
• In this method, if the value of the given field is an array, then this method will be considered each array value as a separate value. For example, if the value of the specified field is [2, [23], 45], then this method considered ‘2’, ‘[23]’, and ’45’ separately.
• In this method, you can also use indexes to enhance performance.

Syntax:

db.Collection_name.distinct(
    field : <string>,
    query : <document>,
    collation : <document> 
)

Parameters:

• The first parameter is the field for which to return distinct values.
• Others are optional.

Optional Parameters:

• query: A query that specifies the documents from which to retrieve the distinct values.
• collation: It specifies the use of the collation for operations. It allows users to specify the language-specific rules for string comparison like rules for lettercase and accent marks. The type of this parameter is a document.

Return Value:

It returns an array of all the distinct values for specified fields that match to the given query.

Examples:

In the following examples, we are working with:

Database: gfg

Collections: student

Document: Three documents contains the details of the students

• Return name of all the student present in the collection:

db.student.distinct("name")

Here, the distinct() method returns the value of the name field.

• Return the distinct value of the embedded field from the given collection:

db.student.distinct("detail.age")

Here, the distinct() method returns the value of the age field.

• Return the distinct value from an array field

db.student.distinct("marks")

Here, the distinct() method returns the value of the marks field.