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How do you remove an array element by its index in MongoDB
To remove array element by its index in MongoDB, you can use $unset and $pull operator. There are two steps to remove array elements from an array.The syntax for the same is as follows:
db.yourCollectionName.update({},{$unset:{"yourArrayListName.yourPosition":yourPositionValue}};
db.yourCollectionName.update({},{$pull:{"yourArrayListName":null}});To understand the above syntax, let us create a collection with document. The query to create a collection with document is as follows:
>db.removeArrayElements.insertOne({"StudentName":"Larry","StudentAge":23,"TechnicalSub
ject":["C","C++","Java","MongoDB"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c6ea4879c4643706aef56d2")
}Display all documents from a collection with the help of find() method. The query is as follows:
> db.removeArrayElements.find().pretty();
The following is the output:
{
"_id" : ObjectId("5c6ea4879c4643706aef56d2"),
"StudentName" : "Larry",
"StudentAge" : 23,
"TechnicalSubject" : [
"C",
"C++",
"Java",
"MongoDB"
]
}Here is the query to remove array element by its index:
> db.removeArrayElements.update({},{$unset:{"TechnicalSubject.3":1}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.removeArrayElements.update({},{$pull:{"TechnicalSubject":null}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Above, we have removed array element “MongoDB”, which is at index 3. Let us display documents from a collection. The query is as follows:
> db.removeArrayElements.find().pretty();
The following is the output:
{
"_id" : ObjectId("5c6ea4879c4643706aef56d2"),
"StudentName" : "Larry",
"StudentAge" : 23,
"TechnicalSubject" : [
"C",
"C++",
"Java"
]
}Look at the above sample output, the index 3 i.e. position 4 has been removed from the array i.e. the element “MongoDB”.
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