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Delete all elements in an array field in MongoDB?
You can use $set operator for this. The syntax is as follows −
db.yourCollectionName.update({}, { $set : {"yourFieldName": [] }} , {multi:true} );To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows −
> db.deleteAllElementsInArrayDemo.insertOne({"InstructorName":"Larry","InstructorTechnicalSubject":["Java","MongoDB"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8fb971d3c9d04998abf00e")
}
> db.deleteAllElementsInArrayDemo.insertOne({"InstructorName":"Mike","InstructorTechnicalSubject":["C","C++","Python"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8fb98ad3c9d04998abf00f")
}Display all documents from a collection with the help of find() method. The query is as follows −
> db.deleteAllElementsInArrayDemo.find().pretty();
The following is the output −
{
"_id" : ObjectId("5c8fb971d3c9d04998abf00e"),
"InstructorName" : "Larry",
"InstructorTechnicalSubject" : [
"Java",
"MongoDB"
]
}
{
"_id" : ObjectId("5c8fb98ad3c9d04998abf00f"),
"InstructorName" : "Mike",
"InstructorTechnicalSubject" : [
"C",
"C++",
"Python"
]
}Here is the query to delete all elements in the array field −
> db.deleteAllElementsInArrayDemo.update({}, { $set : {"InstructorTechnicalSubject": [] }} , {multi:true} );
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })Let us now check all the documents from a collection using find(). The query is as follows −
> db.deleteAllElementsInArrayDemo.find().pretty();
The following is the output. We have deleted all the elements of the “InstructorTechnicalSubject” array field:
{
"_id" : ObjectId("5c8fb971d3c9d04998abf00e"),
"InstructorName" : "Larry",
"InstructorTechnicalSubject" : [ ]
}
{
"_id" : ObjectId("5c8fb98ad3c9d04998abf00f"),
"InstructorName" : "Mike",
"InstructorTechnicalSubject" : [ ]
}
Updated on: 30-Jul-2019
1K+ Views
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