How does Query.prototype.distinct() work in Mongoose?
Last Updated :
17 Mar, 2021
The Query.prototype.distinct() function declares or executes a distinct() operation. And if we pass a callback, then the query executes.
Syntax:
Query.prototype.distinct()
Parameters: This function has three optional parameters ie. field, filter and callback function.
Return Value: This function returns Query Object.
Installing mongoose :
npm install mongoose
After installing the mongoose module, you can check your mongoose version in command prompt using the command.
npm mongoose --version
Now, create a folder and add a file for example, index.js as shown below.
Database: The sample database used here is shown below:
Example 1:
index.js
const mongoose = require( 'mongoose' );
useNewUrlParser: true ,
useCreateIndex: true ,
useUnifiedTopology: true
});
const User = mongoose.model( 'User' , {
name: { type: String },
age: { type: Number }
});
var query = User.distinct( 'age' );
query.exec( function (error,result) {
if (error) console.log(error)
else console.log(result)
})
|
Steps to run the program:
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
[ 10, 25, 5, 34 ]
Example 2:
index.js
const express = require( 'express' );
const mongoose = require( 'mongoose' );
const app = express()
useNewUrlParser: true ,
useCreateIndex: true ,
useUnifiedTopology: true
});
const User = mongoose.model( 'User' , {
name: { type: String },
age: { type: Number }
});
var query = User.distinct( 'name' );
query.exec( function (error,result) {
if (error) console.log(error)
else console.log(result)
})
app.listen(3000, function (error ) {
if (error) console.log(error)
console.log( "Server listening on PORT 3000" )
});
|
Steps to run the program:
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
Server listening on PORT 3000
[ 'Gourav', 'Lalit', 'Piyush', 'Manish' ]
Reference: https://mongoosejs.com/docs/api/query.html#query_Query-distinct
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