MongoDB’s update() and save() methods exaplin in details

MongoDB’s update() and save() methods are used to update document into a collection. The update() method updates the values in the existing document while the save() method replaces the existing document with the document passed in save() method.

MongoDB Update() Method
The update() method updates the values in the existing document.

Syntax
The basic syntax of update() method is as follows −

>db.COLLECTION_NAME.update(SELECTION_CRITERIA, UPDATED_DATA)

Example
Consider the mycol collection has the following data.

{ "_id" : ObjectId(5983548781331adf45ec5), "title":"MongoDB Overview"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}

Following example will set the new title ‘New MongoDB Tutorial’ of the documents whose title is ‘MongoDB Overview’.

>db.mycol.update({‘title’:’MongoDB Overview’},{$set:{‘title’:’New MongoDB Tutorial’}})
>db.mycol.find()
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"New MongoDB Tutorial"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
>
By default, MongoDB will update only a single document. To update multiple documents, you need to set a parameter ‘multi’ to true.

>db.mycol.update({‘title’:’MongoDB Overview’},
{$set:{‘title’:’New MongoDB Tutorial’}},{multi:true})
MongoDB Save() Method
The save() method replaces the existing document with the new document passed in the save() method.

Syntax
The basic syntax of MongoDB save() method is shown below −

>db.COLLECTION_NAME.save({_id:ObjectId(),NEW_DATA})

Example
Following example will replace the document with the _id ‘5983548781331adf45ec7’.

>db.mycol.save(
{
"_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point New Topic",
"by":"Tutorials Point"
}
)
>db.mycol.find()
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"Tutorials Point New Topic",
"by":"Tutorials Point"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
>

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