$last
The $last operator returns the last document from the result sorted by one or more fields
$last
The $last operator sorts documents on one or more fields specified by the query and returns the last document matching the filtering criteria.
Parameters
| Parameter | Description |
|---|---|
expression | The expression to evaluate and return the last document from the result set |
Examples
Consider this sample document from the stores collection.
{
"_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
"name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
"location": {
"lat": -89.2384,
"lon": -46.4012
},
"staff": {
"totalStaff": {
"fullTime": 8,
"partTime": 20
}
},
"sales": {
"totalSales": 75670,
"salesByCategory": [
{
"categoryName": "Wine Accessories",
"totalSales": 34440
},
{
"categoryName": "Bitters",
"totalSales": 39496
},
{
"categoryName": "Rum",
"totalSales": 1734
}
]
},
"promotionEvents": [
{
"eventName": "Unbeatable Bargain Bash",
"promotionalDates": {
"startDate": {
"Year": 2024,
"Month": 6,
"Day": 23
},
"endDate": {
"Year": 2024,
"Month": 7,
"Day": 2
}
},
"discounts": [
{
"categoryName": "Whiskey",
"discountPercentage": 7
},
{
"categoryName": "Bitters",
"discountPercentage": 15
},
{
"categoryName": "Brandy",
"discountPercentage": 8
},
{
"categoryName": "Sports Drinks",
"discountPercentage": 22
},
{
"categoryName": "Vodka",
"discountPercentage": 19
}
]
},
{
"eventName": "Steal of a Deal Days",
"promotionalDates": {
"startDate": {
"Year": 2024,
"Month": 9,
"Day": 21
},
"endDate": {
"Year": 2024,
"Month": 9,
"Day": 29
}
},
"discounts": [
{
"categoryName": "Organic Wine",
"discountPercentage": 19
},
{
"categoryName": "White Wine",
"discountPercentage": 20
},
{
"categoryName": "Sparkling Wine",
"discountPercentage": 19
},
{
"categoryName": "Whiskey",
"discountPercentage": 17
},
{
"categoryName": "Vodka",
"discountPercentage": 23
}
]
}
]
}Example 1: Get the last updated store within a company
To retrieve the more recently updated store within the First Up Consultants company, run a query to fetch all stores within First Up Consultants, sort the documents in ascending order of the lastUpdated field and return the last document from the sorted results.
db.stores.aggregate([{
$match: {
company: {
$in: ["First Up Consultants"]
}
}
}, {
$sort: {
lastUpdated: 1
}
}, {
$group: {
_id: "$company",
lastUpdated: {
$last: "$lastUpdated"
}
}
}])This query returns the following result:
[
{
"_id": "First Up Consultants",
"lastUpdated": "ISODate('2024-12-31T13:01:19.097Z')"
}
]Example 2 - Using the window operator
To retrieve the more recently updated store within each company, run a query to partition the results by the company field and sort the documents within each partition in ascending order of lastUpdated field and return the sorted results per partition.
db.stores.aggregate([{
$setWindowFields: {
partitionBy: "$company",
sortBy: {
lastUpdated: 1
},
output: {
lastUpdatedDateForStore: {
$last: "$lastUpdated",
window: {
documents: ["current", "unbounded"]
}
}
}
}
}])The first result returned by this query is:
[
{
"_id": "First Up Consultants",
"lastUpdated": "ISODate('2024-12-31T13:01:19.097Z')"
}
]