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Get number of updated documents in MongoDB?
To get number of updated documents in MongoDB, you need to use runCommand along with getlasterror.
Let us first create a collection with documents
> db.getNumberOfUpdatedDocumentsDemo.insertOne({"StudentName":"David"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca28c1d6304881c5ce84bad")
}
> db.getNumberOfUpdatedDocumentsDemo.insertOne({"StudentName":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca28c226304881c5ce84bae")
}
> db.getNumberOfUpdatedDocumentsDemo.insertOne({"StudentName":"Robert"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca28c276304881c5ce84baf")
}
> db.getNumberOfUpdatedDocumentsDemo.insertOne({"StudentName":"Ramit"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca28c366304881c5ce84bb0")
}
> db.getNumberOfUpdatedDocumentsDemo.insertOne({"StudentName":"Adam"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca28c436304881c5ce84bb1")
}Following is the query to display all documents from a collection with the help of find() method:
> db.getNumberOfUpdatedDocumentsDemo.find().pretty();
This will produce the following output
{ "_id" : ObjectId("5ca28c1d6304881c5ce84bad"), "StudentName" : "David" }
{ "_id" : ObjectId("5ca28c226304881c5ce84bae"), "StudentName" : "Chris" }
{ "_id" : ObjectId("5ca28c276304881c5ce84baf"), "StudentName" : "Robert" }
{ "_id" : ObjectId("5ca28c366304881c5ce84bb0"), "StudentName" : "Ramit" }
{ "_id" : ObjectId("5ca28c436304881c5ce84bb1"), "StudentName" : "Adam" }Following is the query to update documents
> db.getNumberOfUpdatedDocumentsDemo.update({}, {$set : {"StudentName" : "Carol"}}, true, true);
WriteResult({ "nMatched" : 5, "nUpserted" : 0, "nModified" : 5 })
Now, get the number of updated documents:
> db.runCommand( "getlasterror" );Following is the output displaying n =5 i.e. 5 documents have been updated
{
"connectionId" : 4,
"updatedExisting" : true,
"n" : 5,
"syncMillis" : 0,
"writtenTo" : null,
"err" : null,
"ok" : 1
}Now display all documents from a collection
> db.getNumberOfUpdatedDocumentsDemo.find().pretty();
This will produce the following output
{ "_id" : ObjectId("5ca28c1d6304881c5ce84bad"), "StudentName" : "Carol" }
{ "_id" : ObjectId("5ca28c226304881c5ce84bae"), "StudentName" : "Carol" }
{ "_id" : ObjectId("5ca28c276304881c5ce84baf"), "StudentName" : "Carol" }
{ "_id" : ObjectId("5ca28c366304881c5ce84bb0"), "StudentName" : "Carol" }
{ "_id" : ObjectId("5ca28c436304881c5ce84bb1"), "StudentName" : "Carol" }
Updated on: 30-Jul-2019
154 Views
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