How to Use $all Operator in MongoDB: Syntax and Examples

In MongoDB, the $all operator is used to find documents where an array field contains all the specified elements. You provide an array of values to $all, and MongoDB returns documents whose array field includes every one of those values, regardless of order or extra elements.

Syntax

The $all operator is used inside a query to match documents where the specified array field contains all the given elements.

Syntax parts:

• field: The name of the array field to check.
• $all: Operator that takes an array of values to match.
• The query returns documents where field contains every element in the $all array.

json

{
  "field": { "$all": ["value1", "value2", "..."] }
}

Example

This example shows how to find documents where the tags array contains both "red" and "blue".

javascript

db.products.insertMany([
  { _id: 1, tags: ["red", "blue", "green"] },
  { _id: 2, tags: ["blue", "yellow"] },
  { _id: 3, tags: ["red", "blue"] },
  { _id: 4, tags: ["green", "yellow"] }
])

// Query to find documents where tags contain both "red" and "blue"
db.products.find({ tags: { $all: ["red", "blue"] } })

Output

[
  { _id: 1, tags: ["red", "blue", "green"] },
  { _id: 3, tags: ["red", "blue"] }
]

Common Pitfalls

Common mistakes when using $all include:

• Using $all with a single value instead of an array, which will not work.
• Expecting $all to match documents that contain any one of the values instead of all.
• Confusing $all with $in, which matches any of the values.

javascript

// Wrong: Using $all with a single value (incorrect)
db.products.find({ tags: { $all: "red" } })

// Right: Use an array even for one value
db.products.find({ tags: { $all: ["red"] } })

Quick Reference

Operator	Description	Example Usage
$all	Matches arrays containing all specified elements	{ tags: { $all: ["red", "blue"] } }
$in	Matches arrays containing any of the specified elements	{ tags: { $in: ["red", "blue"] } }
$elemMatch	Matches arrays with elements matching specified criteria	{ tags: { $elemMatch: { $eq: "red" } } }

Key Takeaways

Use $all to find documents where an array contains every specified element.

$all requires an array of values, even if matching only one element.

$all matches all values regardless of order and allows extra elements in the array.

Do not confuse $all with $in; $in matches any one of the values.

Use $all for strict matching of multiple array elements in MongoDB queries.