Mongoose Query.prototype.distinct() API
Last Updated :
09 Jan, 2023
The Mongoose Query API distinct() method is used to find the distinct values for a particular field in a collection and return the response as an array.
Syntax:
Query.prototype.distinct(field, filter, callback)
Parameters: It accepted the following parameters as mentioned above and described below:
- field: It is a string that identifies the field for which to return the distinct values.
- filter: It is an optional mongoose object which is derived from Query.prototype.setOptions().
- callback: It is a callback function that accepts 2 parameters: error and arr.
Return type: It returns a Query object as a response.
Creating node application And Installing Mongoose:
Step 1: Create a node application using the following command:
mkdir folder_name
cd folder_name
npm init -y
touch main.js
Step 2: After completing the Node.js application, Install the required module using the following command:
npm install mongoose
Example 1: In this example, we will use this method to find the distinct values for the field “age” in the collection.
Filename: main.js
Javascript
const mongoose = require( 'mongoose' )
{
dbName: 'event_db' ,
useNewUrlParser: true ,
useUnifiedTopology: true
}, err => err ? console.log(err)
: console.log( 'Connected to database' ));
const personSchema = new mongoose.Schema({
name: {
type: String,
},
age: {
type: Number,
}
});
const personsArray = [
{
name: 'Luffy' ,
age: 20
},
{
name: 'Nami' ,
age: 20,
},
{
name: 'Zoro' ,
age: 35
}
]
const Person = mongoose.model( 'Person' , personSchema);
(async () => {
await Person.insertMany(personsArray);
const res = await Person.distinct( 'age' );
console.log({ res });
})()
|
Step to Run Application: Run the application using the following command from the root directory of the project:
node main.js
Output:
GUI Representation of the Database using MongoDB Compass:
Example 2: In this example, we will use this method to find the distinct values for the field “name” in the collection.
Filename: main.js
Javascript
const mongoose = require( 'mongoose' )
{
dbName: 'event_db' ,
useNewUrlParser: true ,
useUnifiedTopology: true
}, err => err ? console.log(err)
: console.log( 'Connected to database' ));
const personSchema = new mongoose.Schema({
name: {
type: String,
},
age: {
type: Number,
}
});
const personsArray = [
{
name: 'Luffy' ,
age: 20
},
{
name: 'Nami' ,
age: 20,
},
{
name: 'Zoro' ,
age: 35
}
]
const Person = mongoose.model( 'Person' , personSchema);
(async () => {
await Person.insertMany(personsArray);
const res = await Person.distinct( 'name' );
console.log({ res });
})()
|
Step to Run Application: Run the application using the following command from the root directory of the project:
node main.js
Output:
GUI Representation of the Database using MongoDB Compass:
Reference: https://mongoosejs.com/docs/api/query.html#query_Query-distinct
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