How to update field by multiply field value in mongodb?

@jerad 

To update a field by multiplying its current value in MongoDB, you can use the $mul operator in combination with the update() method. Here's an example query that demonstrates how to update a field named "field_name" by multiplying its value by a specific number:

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db.collection.update(
   { }, // filter criteria (empty in this case to match all documents)
   { $mul: { field_name: <multiplier> } }, // update operation using $mul
   { multi: true } // option to update multiple documents
)

In the above query:

• Replace "collection" with the name of your collection.
• Replace "field_name" with the name of the field you want to update.
• Replace "" with the number by which you want to multiply the field's current value.

You can also add a filter criteria within the update() method to target specific documents for the update operation. For example, if you only want to update documents where a specific condition is met, you can add a query filter inside the first parameter of the update() method.

After running this query in the MongoDB shell, all documents in the collection will have their "field_name" field updated by multiplying its current value by the specified multiplier.