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Updating data in MongoDB (part 2)

The updateMany() method allows you to update all documents that satisfy a condition.

The following shows the syntax of the updateMany() method:

db.collection.updateMany(filter, update, options)

In this syntax:

  • The filter is a document that specifies the condition to select the document for update. If you pass an empty document ({}) into the method, it’ll update all the documents the collection.
  • The update is a document that specifies the updates to apply.
  • The options argument provides some options for updates that won’t be covered in this tutorial.

The updateMany() method returns a document that contains multiple fields. The following are the notable ones:

  • The matchedCount stores the number of matched documents.
  • The modifiedCount stores the number of modified documents.

To form the update argument, you typically use the $set operator.

The $set operator replaces the value of a field with a specified value. It has the following syntax:

{ $set: { <field1>: <value1>, <field2>: <value2>, ...}}

If the field doesn’t exist, the $set operator will add the new field with the specified value to the document. If you specify the field with the dot notation e.g., embededDoc.field and the field does not exist, the $set operator will create the embedded document.

Launch mongo shell from the Terminal on Linux and connect to the productdb database on the local MongoDB server: mongosh productdb We’ll use the following products collection for the projection examples:

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],"inventory":[{ qty: 1200,"warehouse": "San Jose"}]},
    { "_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],"inventory":[{ qty: 300,"warehouse": "San Francisco"}]},
    { "_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],"inventory":[{ qty: 400,"warehouse": "San Jose"},{ qty: 200,"warehouse": "San Francisco"}]},
    { "_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],"inventory":[{ qty: 1200,"warehouse": "San Mateo"}]},
    { "_id" : 5, "name" : "SmartPhone", "price" : 599,"releaseDate": ISODate("2022-09-14"), "spec" : { "ram" : 4, "screen" : 5.7, "cpu" : 1.66 },"color":["white","orange","gold","gray"],"storage":[128,256]}
 ])

Using the MongoDB updateMany() method to update multiple documents

The following example uses the updateMany() method to update the documents where the value of the price field is 899:

db.products.updateMany(
    {  price: 899}, 
    { $set: {  price: 895 }}
)

In this query:

The { price : 899 } is the filter argument that specified the documents to update.

The { $set: { price: 895} } specifies the update to apply, which uses the $set operator to set the value of the price field to 895. To check the update, you can use the find() method to select the documents where the value of the price field is 895 as follows:

db.products.find({
    price: 895
}, {
    name: 1,
    price: 1
})

Using the updateMany() method to update embedded documents

The following query uses the find() method to select the documents where the value in the price field is greater than 700:

db.products.find({
    price: { $gt: 700}
}, {
    name: 1,
    price: 1,
    spec: 1
})

The following example uses the updateMany() method to update the values of the ram, screen, and cpu fields in the spec embedded documents of these documents:

db.products.updateMany({
    price: { $gt: 700}
}, {
    $set: {
        "spec.ram": 32,
        "spec.screen": 9.8,
        "spec.cpu": 5.66
    }
})

Using the MongoDB updateMany() method to update array elements

The following example uses the updateMany() method to update the first and second elements of the storage array of the documents where the _id is 1, 2 and 3:

db.products.updateMany({
    _id: {
        $in: [1, 2, 3]
    }
}, {
    $set: {
        "storage.0": 16,
        "storage.1": 32
    }
})

If your query the documents whose _id is 1, 2, and 3 from the products collection, you’ll see that the first and second elements of the storage array have been updated:

db.products.find(
   { _id: { $in: [1,2,3]}}, 
   { name: 1, storage: 1}
)

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