Update Documents: Part 1

Update single document

We use the below commands to update a single document.

db.<collection-name>.updateOne(
    <filter query>,
    <update document>,
    <options>
);

Filter query

filter query is used to build criteria to fetch documents. This should return only one document if used with the updateOne method.

Update document

The updated document contains modifications that need to apply to the document. Through this document, we can:

• Replace a field value
• Add a new field
• Increment or decrement a number
• Add a new value in the array
• Remove a value from the array
• Perform modification on the document returned by filter query

Options

Options allow us to be more specific about what elements we want to update on a given document. Below are some common examples.

• Options.upsert: This accepts only boolean type values and the default value is false. This is an optional parameter. When it’s true and the filter query doesn’t find any record, it inserts a new document.
• writeConcern: This was explained in the lesson Write Concern.
• collation: This was explained in the lesson Collation and Hint.
• arrayFilters: This allows us to specify an array of filter documents that determine which array elements are modified during an update. This concept is too advanced to cover in this course, so we’ll focus on the other elements of these options.

First, let’s insert some documents to perform update operations.

The above code returns insertedId, which is the primary key of the document. This is what we’ll use to perform the update operations.

Example:

The below command updates the status of the matching task with provided _id.

The below output shows that the filter query matched one document, (matchedCount: 1), and an update operation was applied to one document, (modifiedCount: 1).

{
  acknowledged: true,
  insertedId: null,
  matchedCount: 1,
  modifiedCount: 1,
  upsertedCount: 0
}

We can use the below command to check stored documents.

db.tasks.find();

Update multiple documents

We use the below commands to update multiple documents.

db.<collection-name>.updateMany(
    <filter query>,
    <update document>,
    <options>
);

The arguments filter query, update document, and options behave the same as they do for updateOne.

All the documents returned from the filter query are updated by the update document parameter. In the below example, the status is updated on the documents returned by filter query.

The below output shows that the filter query matched two documents, (matchedCount: 2), and it performed an update operation on two documents, (modifiedCount: 2).

{
  acknowledged: true,
  insertedId: null,
  matchedCount: 2,
  modifiedCount: 2,
  upsertedCount: 0
}

We can also update documents using the bulkWrite method.

Let’s insert some documents and practice the update operation in the terminal below.