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Unset an attribute from a single array element in MongoDB?
Use $unset operator to unset an attribute. Let us first create a collection with documents −
> db.unsetAnAttributeDemo.insertOne(
... {
... _id: 1,
... "StudentDetails": [
... {
... "StudentFirstName": "Ramit",
... "StudentCountryName":"UK"
... },
... {
... "StudentFirstName": "Bob",
... "StudentCountryName":"US"
... },
... {
... "StudentFirstName": "Carol",
... "StudentCountryName":"AUS"
...
... }
... ]
... }
... );
{ "acknowledged" : true, "insertedId" : 1 }Following is the query to display all documents from the collection with the help of find() method −
> db.unsetAnAttributeDemo.find().pretty();
This will produce the following output −
{
"_id" : 1,
"StudentDetails" : [
{
"StudentFirstName" : "Ramit",
"StudentCountryName" : "UK"
},
{
"StudentFirstName" : "Bob",
"StudentCountryName" : "US"
},
{
"StudentFirstName" : "Carol",
"StudentCountryName" : "AUS"
}
]
}Following is the query to unset an attribute from a single array element. The attribute “StudentCountryName” with value “AUS” will unset −
> db.unsetAnAttributeDemo.update({"StudentDetails.StudentCountryName": "AUS"}, {$unset:
{"StudentDetails.$.StudentCountryName": 1}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Let us display the document from the collection to check that attribute StudentCountryName with value “AUS” has been cleared or not −
> db.unsetAnAttributeDemo.find().pretty();
This will produce the following output −
{
"_id" : 1,
"StudentDetails" : [
{
"StudentFirstName" : "Ramit",
"StudentCountryName" : "UK"
},
{
"StudentFirstName" : "Bob",
"StudentCountryName" : "US"
},
{
"StudentFirstName" : "Carol"
}
]
}
Updated on 30-Jul-2019 22:30:25
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