MongoDB $not

Summary: in this tutorial, you’ll learn how to use the MongoDB $not operator to perform a logical NOT operator.

Introduction to the MongoDB $not operator

The following shows the syntax of the $not operator:

{ field: { $not: { <expression> } } }

The $not operator is a logical query operator that performs a logical NOT operation on a specified <expression> and selects documents that do not match the <expression>. This includes documents that do not contain the field.

MongoDB $not operator examples

We’ll use the following products collection:

db.products.insertMany([
	{ "_id" : 1, "name" : "xPhone", "price" : 799, "releaseDate" : ISODate("2011-05-14T00:00:00Z"), "spec" : { "ram" : 4, "screen" : 6.5, "cpu" : 2.66 }, "color" : [ "white", "black" ], "storage" : [ 64, 128, 256 ] },
	{ "_id" : 2, "name" : "xTablet", "price" : 899, "releaseDate" : ISODate("2011-09-01T00:00:00Z"), "spec" : { "ram" : 16, "screen" : 9.5, "cpu" : 3.66 }, "color" : [ "white", "black", "purple" ], "storage" : [ 128, 256, 512 ] },
	{ "_id" : 3, "name" : "SmartTablet", "price" : 899, "releaseDate" : ISODate("2015-01-14T00:00:00Z"), "spec" : { "ram" : 12, "screen" : 9.7, "cpu" : 3.66 }, "color" : [ "blue" ], "storage" : [ 16, 64, 128 ] },
	{ "_id" : 4, "name" : "SmartPad", "price" : 699, "releaseDate" : ISODate("2020-05-14T00:00:00Z"), "spec" : { "ram" : 8, "screen" : 9.7, "cpu" : 1.66 }, "color" : [ "white", "orange", "gold", "gray" ], "storage" : [ 128, 256, 1024 ] },
	{ "_id" : 5, "name" : "SmartPhone", "price" : 599, "releaseDate" : ISODate("2022-09-14T00:00:00Z"), "spec" : { "ram" : 4, "screen" : 9.7, "cpu" : 1.66 }, "color" : [ "white", "orange", "gold", "gray" ], "storage" : [ 128, 256 ] },
	{ "_id" : 6, "name" : "xWidget", "spec" : { "ram" : 64, "screen" : 9.7, "cpu" : 3.66 }, "color" : [ "black" ], "storage" : [ 1024 ] }
])

1) Using MongoDB $not operator to select documents

The following example shows how to use the $not operator to find documents where:

• the price field is not greater than 699.
• do not contain the price field.

db.products.find({
    price: {
        $not: {
            $gt: 699
        }
    }
}, {
    name: 1,
    price: 1
})

It returned the following documents:

{ "_id" : 4, "name" : "SmartPad", "price" : 699 }
{ "_id" : 5, "name" : "SmartPhone", "price" : 599 }
{ "_id" : 6, "name" : "xWidget" }

Notice that the { $not: { $gt: 699 } } is different from the $lte operator. The { $lte : 699 } returns documents where the price field exists and its value is less than or equal to 699.

The following example uses the $lte operator:

db.products.find({
    price: {
        $lte: 699
    }
}, {
    name: 1,
    price: 1
})

It returned the following documents:

{ "_id" : 4, "name" : "SmartPad", "price" : 699 }
{ "_id" : 5, "name" : "SmartPhone", "price" : 599 }

As you can see clearly from the output, the result of the query that uses the $lte operator does not include the documents where the price field does not exist.

2) Using MongoDB $not operator to select documents based on expressions

The following example uses the $not operator to select documents from the products collection where the value of the field does not match the regular expression /^smart+/i:

db.products.find({
    name: {
        $not: /^Smart+/
    }
}, {
    name: 1
})

The regular expression /^Smart+/ matches any string that starts with the string smart and is followed by any number of characters.

The query returns the following documents:

{ "_id" : 1, "name" : "xPhone" }
{ "_id" : 2, "name" : "xTablet" }
{ "_id" : 6, "name" : "xWidget" }

Summary

• Use the MongoDB $not operator to performs a logical NOT operation on a specified <expression> and selects documents that do not match the <expression>.