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$in

$in: The $in operator selects the documents where the value of a field equals any value in the specified array.

Compatibility

You can use $in for deployments hosted in the following environments:

MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Syntax

The $in operator has the following form:

{ field: { $in: [ <value1>, <value2>, ... <valueN> ] } }

For comparison of different BSON type values, see the specified BSON comparison order.

If field has an array, the $in operator selects the documents whose field has an array that contains at least one element that matches a value in the specified array. For example, <value1>, <value2>, and so on.

$in compares each parameter to each document in the collection, which can cause performance issues. To improve performance:

Limit the number of parameters passed to $in to tens of values. Using hundreds of parameters can negatively impact query performance.
Create an index on the field you want to query.

Note

This document describes the $in query operator. For the $in aggregation operator, see $in (expression operator).

Query Data on Atlas by Using MongoDB Search

For data stored in MongoDB Atlas, you can use the MongoDB Search in Operator operator when running $search queries. Running $in after $search is less performant than running $search with the in Operator operator.

To learn more about the MongoDB Search version of this operator, see the in Operator operator in the Atlas documentation.

Examples

To create the inventory collection used in the examples, run:

db.inventory.insertMany( [
   { item: "Pens", quantity: 350, tags: [ "school", "office" ] },
   { item: "Erasers", quantity: 15, tags: [ "school", "home" ] },
   { item: "Maps", tags: [ "office", "storage" ] },
   { item: "Books", quantity: 5, tags: [ "school", "storage", "home" ] }
] )

Match Values

This query selects documents in the inventory collection where the value of the quantity field is 5 or 15:

db.inventory.find( { quantity: { $in: [ 5, 15 ] } }, { _id: 0 } )

The output:

{ item: 'Erasers', quantity: 15, tags: [ 'school', 'home' ] },
{ item: 'Books', quantity: 5, tags: [ 'school', 'storage', 'home' ] }

Although you can write the query using the $or operator, use the $in operator rather than the $or operator when performing equality checks on the same field.

Match Values in an Array

The following updateMany() operation sets the exclude field to false when the tags array has at least one element that matches either "home" or "school":

db.inventory.updateMany(
   { tags: { $in: [ "home", "school" ] } },
   { $set: { exclude: false } }
)

Example output:

{
   item: 'Pens',
   quantity: 350,
   tags: [ 'school', 'office' ],
   exclude: false
 },
 {
   item: 'Erasers',
   quantity: 15,
   tags: [ 'school', 'home' ],
   exclude: false
 },
 {
   item: 'Books',
   quantity: 5,
   tags: [ 'school', 'storage', 'home' ],
   exclude: false
 }

For additional examples on querying arrays, see:

For additional examples on querying, see Query Documents.

Use `$in` with a Regular Expression

The $in operator can select documents using regular expressions of the form /pattern/. You cannot use $regex expressions inside $in.

This query selects documents in the inventory collection where the tags field starts with be or st:

db.inventory.find( { tags: { $in: [ /^be/, /^st/ ] } } )

The query selects all documents in the inventory collection where the tags field has either a string that starts with be or st or an array with at least one element that starts with be or st.

Learn More

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$gte

$lt

Compatibility

Syntax

Note

Query Data on Atlas by Using MongoDB Search

Examples

Match Values

Match Values in an Array

Use $in with a Regular Expression

Learn More

Use `$in` with a Regular Expression