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(PDF).
$in
The $in aggregation operator checks if a specified value exists within an array. It returns true if the value is found in the array, and false otherwise.
Parameters
Example (MongoDB Shell)
The following example demonstrates using the $in operator to check if a specific skill exists in each employee's skill set.
Create sample documents
db.employees.insertMany([
{ _id: 1, name: "Sarah", skills: ["Python", "JavaScript", "SQL"] },
{ _id: 2, name: "Mike", skills: ["Java", "C++", "Go"] },
{ _id: 3, name: "Emma", skills: ["Python", "Ruby", "Rust"] }
]);
Query example
db.employees.aggregate([
{
$project: {
name: 1,
hasPython: { $in: ["Python", "$skills"] }
}
}
]);
Output
[
{ _id: 1, name: 'Sarah', hasPython: true },
{ _id: 2, name: 'Mike', hasPython: false },
{ _id: 3, name: 'Emma', hasPython: true }
]
Code examples
To view a code example for using the $in aggregation operator, choose the tab for the language that you want to use:
- Node.js
-
const { MongoClient } = require('mongodb');
async function example() {
const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
const db = client.db('test');
const collection = db.collection('employees');
const result = await collection.aggregate([
{
$project: {
name: 1,
hasPython: { $in: ["Python", "$skills"] }
}
}
]).toArray();
console.log(result);
await client.close();
}
example();
- Python
-
from pymongo import MongoClient
def example():
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
db = client['test']
collection = db['employees']
result = list(collection.aggregate([
{
'$project': {
'name': 1,
'hasPython': { '$in': ['Python', '$skills'] }
}
}
]))
print(result)
client.close()
example()