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$lt![](/docs/v5.3/assets/link.svg)
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Definition![](/docs/v5.3/assets/link.svg)
$lt
Syntax:
{ field: { $lt: value } }
$lt
selects the documents where the value of thefield
is less than (i.e.<
) the specifiedvalue
.For most data types, comparison operators only perform comparisons on fields where the BSON type matches the query value's type. MongoDB supports limited cross-BSON comparison through Type Bracketing.
Examples![](/docs/v5.3/assets/link.svg)
The following examples use the inventory
collection. Create the
collection:
db.inventory.insertMany( [ { "item": "nuts", "quantity": 30, "carrier": { "name": "Shipit", "fee": 3 } }, { "item": "bolts", "quantity": 50, "carrier": { "name": "Shipit", "fee": 4 } }, { "item": "washers", "quantity": 10, "carrier": { "name": "Shipit", "fee": 1 } } ] )
Match Document Fields![](/docs/v5.3/assets/link.svg)
Select all documents in the inventory
collection where quantity
is less than 20
:
db.inventory.find( { quantity: { $lt: 20 } } )
Example output:
{ _id: ObjectId("61ba634dfe687fce2f04241f"), item: 'washers', quantity: 10, carrier: { name: 'Shipit', fee: 1 } }
Perform an Update Based on Embedded Document Fields![](/docs/v5.3/assets/link.svg)
The following example sets the price
field based on a $lt
comparison against a field in an embedded document.
db.inventory.updateMany( { "carrier.fee": { $lt: 20 } }, { $set: { price: 9.99 } } )
Example output:
{ _id: ObjectId("61ba634dfe687fce2f04241d"), item: 'nuts', quantity: 30, carrier: { name: 'Shipit', fee: 3 }, price: 9.99 }, { _id: ObjectId("61ba634dfe687fce2f04241e"), item: 'bolts', quantity: 50, carrier: { name: 'Shipit', fee: 4 }, price: 9.99 }, { _id: ObjectId("61ba634dfe687fce2f04241f"), item: 'washers', quantity: 10, carrier: { name: 'Shipit', fee: 1 }, price: 9.99 }
This updateMany()
operation searches for an
embedded document, carrier
, with a subfield named fee
. It sets
{ price: 9.99 }
in each document where fee
has a value less than
20.
To set the value of the price
field in only the first document
where carrier.fee
is less than 20, use
updateOne()
.