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How to search for a record (field) and then delete it in MongoDB?
To search for a field, use $exists and to delete it, use $unset. The $unset operator in MongoDB deletes a particular field.
Let us create a collection with documents −
> db.demo562.insertOne({"Name":"Chris","Age":21});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8f4ae854b4472ed3e8e872")
}
> db.demo562.insertOne({"Age":20});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8f4ae954b4472ed3e8e873")
}
> db.demo562.insertOne({"Name":"David","Age":23});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8f4aea54b4472ed3e8e874")
}Display all documents from a collection with the help of find() method −
> db.demo562.find();
This will produce the following output −
{ "_id" : ObjectId("5e8f4ae854b4472ed3e8e872"), "Name" : "Chris", "Age" : 21 }
{ "_id" : ObjectId("5e8f4ae954b4472ed3e8e873"), "Age" : 20 }
{ "_id" : ObjectId("5e8f4aea54b4472ed3e8e874"), "Name" : "David", "Age" : 23 }Following is the query to search for a record and then delete it −
> db.demo562.update( {Name:{$exists:true} },{ $unset: {"Name":""}},{multi:true});
WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })Display all documents from a collection with the help of find() method −
> db.demo562.find();
This will produce the following output −
{ "_id" : ObjectId("5e8f4b6654b4472ed3e8e875"), "Age" : 21 }
{ "_id" : ObjectId("5e8f4b6754b4472ed3e8e876"), "Age" : 20 }
{ "_id" : ObjectId("5e8f4b6854b4472ed3e8e877"), "Age" : 23 }
Updated on: 14-May-2020
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