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How to pull all elements from an array in MongoDB without any condition?
You can use $set operator for this. Let us first create a collection with documents −
> db.pullAllElementDemo.insertOne(
... {
... "StudentId":101,
... "StudentDetails" : [
... {
...
... "StudentName": "Carol",
... "StudentAge":21,
... "StudentCountryName":"US"
... },
... {
... "StudentName": "Chris",
... "StudentAge":24,
... "StudentCountryName":"AUS"
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ccdd9c8685b30d09a7111e4")
}
> db.pullAllElementDemo.insertOne(
... {
... "StudentId":102,
... "StudentDetails" : [
... {
...
... "StudentName": "Robert",
... "StudentAge":27,
... "StudentCountryName":"UK"
... },
... {
... "StudentName": "David",
... "StudentAge":23,
... "StudentCountryName":"US"
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ccdd9f7685b30d09a7111e5")
}Following is the query to display all documents from a collection with the help of find() method −
> db.pullAllElementDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5ccdd9c8685b30d09a7111e4"),
"StudentId" : 101,
"StudentDetails" : [
{
"StudentName" : "Carol",
"StudentAge" : 21,
"StudentCountryName" : "US"
},
{
"StudentName" : "Chris",
"StudentAge" : 24,
"StudentCountryName" : "AUS"
}
]
}
{
"_id" : ObjectId("5ccdd9f7685b30d09a7111e5"),
"StudentId" : 102,
"StudentDetails" : [
{
"StudentName" : "Robert",
"StudentAge" : 27,
"StudentCountryName" : "UK"
},
{
"StudentName" : "David",
"StudentAge" : 23,
"StudentCountryName" : "US"
}
]
}Following is the query to pull all elements from array in MongoDB without any condition. Here, we have removed StudentDetails with StudentId 102 using $set −
> db.pullAllElementDemo.update( {StudentId:102}, { "$set": { "StudentDetails": [] }} );
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Let is display all documents from the above collection to check those specific elements from an array have been pulled out or not −
> db.pullAllElementDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5ccdd9c8685b30d09a7111e4"),
"StudentId" : 101,
"StudentDetails" : [
{
"StudentName" : "Carol",
"StudentAge" : 21,
"StudentCountryName" : "US"
},
{
"StudentName" : "Chris",
"StudentAge" : 24,
"StudentCountryName" : "AUS"
}
]
}
{
"_id" : ObjectId("5ccdd9f7685b30d09a7111e5"),
"StudentId" : 102,
"StudentDetails" : [ ]
}
Updated on: 30-Jul-2019
279 Views
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