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‎reference/operators/array-update/$.md‎

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---
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title: $
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description: The $ positional operator identifies an element in an array to update without explicitly specifying the position of the element in the array.
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type: operators
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category: array-update
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---
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# $
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The `$` positional operator identifies an element in an array to update without explicitly specifying the position of the element in the array. The `$` operator acts as a placeholder for the first element that matches the query condition, and the array field must appear as part of the query document.
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## Syntax
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```javascript
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db.collection.updateOne(
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{ <array>: <value> },
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{ <update operator>: { "<array>.$": <value> } }
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)
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```
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## Parameters
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| Parameter | Description |
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| --- | --- |
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| **`array`** | The array field that contains the element to update. Must be part of the query condition. |
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| **`value`** | The value used to match the array element in the query condition. |
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| **`update operator`** | The update operator to apply (for example, `$set`, `$inc`, `$unset`). |
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## Examples
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Consider this sample document from the stores collection.
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```json
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{
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"_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
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"name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
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"location": {
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"lat": -89.2384,
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"lon": -46.4012
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},
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"staff": {
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"totalStaff": {
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"fullTime": 8,
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"partTime": 20
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}
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},
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"sales": {
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"totalSales": 75670,
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"salesByCategory": [
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{
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"categoryName": "Wine Accessories",
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"totalSales": 34440
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},
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{
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"categoryName": "Bitters",
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"totalSales": 39496
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},
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{
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"categoryName": "Rum",
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"totalSales": 1734
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}
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]
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},
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"promotionEvents": [
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{
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"eventName": "Unbeatable Bargain Bash",
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"promotionalDates": {
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"startDate": {
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"Year": 2024,
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"Month": 6,
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"Day": 23
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},
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"endDate": {
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"Year": 2024,
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"Month": 7,
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"Day": 2
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}
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},
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"discounts": [
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{
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"categoryName": "Whiskey",
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"discountPercentage": 7
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},
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{
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"categoryName": "Bitters",
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"discountPercentage": 15
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},
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{
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"categoryName": "Brandy",
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"discountPercentage": 8
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},
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{
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"categoryName": "Sports Drinks",
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"discountPercentage": 22
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},
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{
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"categoryName": "Vodka",
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"discountPercentage": 19
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}
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]
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},
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{
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"eventName": "Steal of a Deal Days",
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"promotionalDates": {
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"startDate": {
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"Year": 2024,
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"Month": 9,
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"Day": 21
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},
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"endDate": {
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"Year": 2024,
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"Month": 9,
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"Day": 29
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}
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},
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"discounts": [
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{
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"categoryName": "Organic Wine",
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"discountPercentage": 19
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},
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{
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"categoryName": "White Wine",
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"discountPercentage": 20
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},
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{
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"categoryName": "Sparkling Wine",
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"discountPercentage": 19
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},
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{
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"categoryName": "Whiskey",
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"discountPercentage": 17
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},
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{
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"categoryName": "Vodka",
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"discountPercentage": 23
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}
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]
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}
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]
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}
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```
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### Example 1: Project the first element of an array, matching the condition
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This query returns the first element within the `salesByCategory` array, for `DJ` equipment with `totalSales` greater than 35000.
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```javascript
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db.stores.find({
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"sales.salesByCategory": {
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$elemMatch: {
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categoryName: {
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$regex: "^DJ"
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}
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}
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},
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"sales.salesByCategory.totalSales": {
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$gt: 35000
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}
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}, {
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"sales.salesByCategory.$": 1
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}).limit(2)
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```
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The first two results returned by this query are:
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```json
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[
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{
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"_id": "d3c9df51-41bd-4b4e-a26b-b038d9cf8b45",
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"sales": {
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"salesByCategory": [
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{
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"categoryName": "DJ Speakers",
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"totalSales": 36972
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}
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]
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}
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},
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{
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"_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
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"sales": {
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"salesByCategory": [
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{
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"categoryName": "DJ Headphones",
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"totalSales": 35911
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}
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]
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}
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}
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]
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```
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### Example 2: Update discount percentage for a specific category
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This query updates the discount percentage for "Desks" category in the first matching promotion event.
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```javascript
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db.stores.updateOne(
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{
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_id: "905d1939-e03a-413e-a9c4-221f74055aac",
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"promotionEvents.discounts.categoryName": "Desks"
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},
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{
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$set: { "promotionEvents.$.discounts.$[elem].discountPercentage": 25 }
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},
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{
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arrayFilters: [{ "elem.categoryName": "Desks" }]
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}
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)
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```
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### Example 3: Update sales category total
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This query updates the total sales for a specific category using the `$ (positional operator)`.
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```javascript
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db.stores.updateOne(
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{
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_id: "905d1939-e03a-413e-a9c4-221f74055aac",
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"sales.salesByCategory.categoryName": "Desk Lamps"
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},
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{
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$inc: { "sales.salesByCategory.$.totalSales": 1000 }
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}
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)
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```

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