MongoDB query to update each field of documents in collection with a formula?

To update each field of documents in collection with a formula, use MongoDB update(). Let us create a collection with documents −

> db.demo749.insertOne({"details":[{"id":1,a:10},{"id":2,a:5},{"id":3,a:20}]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5eae6fb0a930c785c834e565")
}

Display all documents from a collection with the help of find() method −

> db.demo749.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5eae6fb0a930c785c834e565"),
   "details" : [
      {
         "id" : 1,
         "a" : 10
      },
      {
         "id" : 2,
         "a" : 5
      },
      {
         "id" : 3,
         "a" : 20
      }
   ]
}

Following is the query to update each field of documents in collection with a formula −

> db.demo749.update(
...    {
...
...    },
...    {
...       $mul: { "details.$[].a": 2/5}
...    },
...    { multi:true}
... )
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Display all documents from a collection with the help of find() method −

> db.demo749.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5eae6fb0a930c785c834e565"),
   "details" : [
      {
         "id" : 1,
         "a" : 4
      },
      {
         "id" : 2,
         "a" : 2
      },
      {
         "id" : 3,
         "a" : 8
      }
   ]
}

AmitDiwan

Updated on 30-Jun-2020 08:11:21

• Related Questions & Answers
• MongoDB query to update array with another field?
• How to update many documents with one query in MongoDB?
• How to Update multiple documents in a MongoDB collection using Java?
• How to update or modify the existing documents of a collection in MongoDB?
• MongoDB query to collectively match intersection of documents against a field
• MongoDB query to update a specific document from a collection
• Update salary field value with 10 percent of each employee in MongoDB
• How to update a single field in a capped collection in MongoDB?
• MongoDB query to update all documents matching specific IDs
• Get the maximum mark records from a collection with documents in MongoDB query
• Find all duplicate documents in a MongoDB collection by a key field?
• MongoDB query to add up the values of a specific field in documents
• How to add a new field to all the documents in a MongoDB collection
• MongoDB concurrent update with sub collection?
• MongoDB query to match each element in a documents array to a condition?