MongoDB $lt

Summary: in this tutorial, you will learn how to use the MongoDB $lt operator to select documents where the value of a field is less than (<) a specified value.

Introduction to the MongoDB $lt operator

The $lt operator is a comparison query operator that allows you to select the documents where the value of a field is less than a specified value.

Here is the syntax of the $lt operator:

{field: {$lt: value} }

MongoDB $lt operator examples

We’ll use the following products collection:

db.products.insertMany([
    { "_id" : 1, "name" : "xPhone", "price" : 799, "releaseDate": ISODate("2011-05-14"), "spec" : { "ram" : 4, "screen" : 6.5, "cpu" : 2.66 },"color":["white","black"],"storage":[64,128,256]},
    { "_id" : 2, "name" : "xTablet", "price" : 899, "releaseDate": ISODate("2011-09-01") , "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("2015-01-14"), "spec" : { "ram" : 12, "screen" : 9.7, "cpu" : 3.66 },"color":["blue"],"storage":[16,64,128]},
    { "_id" : 4, "name" : "SmartPad", "price" : 699, "releaseDate": ISODate("2020-05-14"),"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("2022-09-14"), "spec" : { "ram" : 4, "screen" : 9.7, "cpu" : 1.66 },"color":["white","orange","gold","gray"],"storage":[128,256]}
 ])

1) Using $lt operator to select documents where a field is less than a specified value

The following example uses the $lt operator to select documents from the products collection where price is less than 799:

db.products.find({
    price: {
        $lt: 799
    }
}, {
    name: 1,
    price: 1
})

Output:

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

2) Using the $lt operator to check if a field in an embedded document is less than a value

The following query uses $lt operator to select documents where the value of the screen field in the spec document is less than 7:

db.products.find({
    "spec.screen": {
        $lt: 7
    }
}, {
    name: 1,
    "spec.screen": 1
})

Output:

{ "_id" : 1, "name" : "xPhone", "spec" : { "screen" : 6.5 } }
{ "_id" : 5, "name" : "SmartPhone", "spec" : { "screen" : 5.7 } }

3) Using the $lt operator to check if an array element is greater than or equal to a value

The following example uses the $lt operator to query the products collection to find all documents where the array storage has at least one element less than 128:

db.products.find({
    storage: {
        $lt: 128
    }
}, {
    name: 1,
    storage: 1
})

The query returned the following documents:

{ "_id" : 1, "name" : "xPhone", "storage" : [ 64, 128, 256 ] }
{ "_id" : 3, "name" : "SmartTablet", "storage" : [ 16, 64, 128 ] }

4) Using the $lt operator to check if a field is before a date

The following query uses the $lt operator to select documents from the products collection to find all documents where the release date before 2015-01-01:

db.products.find({
    "releaseDate": {
        $lt: new ISODate('2015-01-01')
    }
}, {
    name: 1,
    releaseDate: 1
})

The query returned the following documents:

{ "_id" : 1, "name" : "xPhone", "releaseDate" : ISODate("2011-05-14T00:00:00Z") }
{ "_id" : 2, "name" : "xTablet", "releaseDate" : ISODate("2011-09-01T00:00:00Z") }

Summary

• Use the $lt operator to select documents where a field is less a specified value.