How to update an already existing field in mongodb?

@lew 

To update an already existing field in MongoDB, you can use the updateOne or updateMany method in combination with the $set operator. Here's how to do it:

1. Update a single document:

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db.collection.updateOne(
   { _id: ObjectId("document_id") },
   { $set: { field_to_update: new_value } }
)

Replace collection with the name of your collection, document_id with the ID of the document you want to update, field_to_update with the name of the field you want to update, and new_value with the new value for the field.

1. Update multiple documents that match a certain condition:

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db.collection.updateMany(
   { field_to_update: old_value },
   { $set: { field_to_update: new_value } }
)

Replace collection with the name of your collection, field_to_update with the name of the field you want to update, old_value with the current value of the field, and new_value with the new value for the field.

These commands will update the specified field in the document(s) in your MongoDB collection. Make sure to replace the placeholder values with your actual document IDs, field names, and new values.