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How to remove a field completely from a MongoDB document?
You can use $unset operator to remove a field completely from a MongoDb document. The syntax is as follows:
db.yourCollectionName.update({}, {$unset: {yourFieldName:1}}, false, true);To understand the above syntax, let us create a collection with some documents. The query to create a collection with documents are as follows:
>
db.removeFieldCompletlyDemo.insertOne({"StudentName":"Larry","StudentFavouriteSubject":
["Java","C","C++","Python"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6ef55a6fd07954a48906a3")
}
>
db.removeFieldCompletlyDemo.insertOne({"StudentName":"Mike","StudentFavouriteSubject":
["Javascript","HTML5","CSS3"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6ef57b6fd07954a48906a4")
}
>
db.removeFieldCompletlyDemo.insertOne({"StudentName":"Sam","StudentFavouriteSubject":
["MongoDB","MySQL","SQL Server"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6ef59c6fd07954a48906a5")
}Display all documents from a collection with the help of find() method. The query is as follows:
> db.removeFieldCompletlyDemo.find().pretty();
The following is the output:
{
"_id" : ObjectId("5c6ef55a6fd07954a48906a3"),
"StudentName" : "Larry",
"StudentFavouriteSubject" : [
"Java",
"C",
"C++",
"Python"
]
}
{
"_id" : ObjectId("5c6ef57b6fd07954a48906a4"),
"StudentName" : "Mike",
"StudentFavouriteSubject" : [
"Javascript",
"HTML5",
"CSS3"
]
}
{
"_id" : ObjectId("5c6ef59c6fd07954a48906a5"),
"StudentName" : "Sam",
"StudentFavouriteSubject" : [
"MongoDB",
"MySQL",
"SQL Server"
]
}Remove field "StudentFavouriteSubject" from documents. The query is as follows:
> db.removeFieldCompletlyDemo.update({}, {$unset: {StudentFavouriteSubject:1}}, false, true);
WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })We have removed the field "StudentFavouriteSubject" from documents. Let us now display all documents from a collection to verify.
The query is as follows:
> db.removeFieldCompletlyDemo.find().pretty();
The following is the output:
{ "_id" : ObjectId("5c6ef55a6fd07954a48906a3"), "StudentName" : "Larry" }
{ "_id" : ObjectId("5c6ef57b6fd07954a48906a4"), "StudentName" : "Mike" }
{ "_id" : ObjectId("5c6ef59c6fd07954a48906a5"), "StudentName" : "Sam" }
Updated on: 30-Jul-2019
709 Views
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