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Clearing items in a nested MongoDB array?
To clear items in a nested array, use the $set operator. Let us first create a collection. Following is the query to create a collection with documents
> db.clearingItemsInNestedArrayDemo.insertOne( {
...
... "StudentName" : "John",
... "StudentDetails" : [
... {
... "ProjectName" : "Online Banking",
... "ProjectDetails" : [
... {
... "TechnologyUsed" : "Java",
... "TeamSize":5
... },
...
... ]
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9930b4330fd0aa0d2fe4ce")
}Following is the query to display all documents from a collection with the help of find() method
> db.clearingItemsInNestedArrayDemo.find().pretty();
This will produce the following output
{
"_id" : ObjectId("5c9930b4330fd0aa0d2fe4ce"),
"StudentName" : "John",
"StudentDetails" : [
{
"ProjectName" : "Online Banking",
"ProjectDetails" : [
{
"TechnologyUsed" : "Java",
"TeamSize" : 5
}
]
}
]
}Following is the query to clear items in a nested array
> db.clearingItemsInNestedArrayDemo.update({"StudentName": "John"}, {"$set": {"StudentDetails": []}});
Updated 1 existing record(s) in 4ms
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Now check the documents from the collection once again to verify that the items have been cleared from the nested array or not. Following is the query
> db.clearingItemsInNestedArrayDemo.find().pretty();
This will produce the following output
{
"_id" : ObjectId("5c9930b4330fd0aa0d2fe4ce"),
"StudentName" : "John",
"StudentDetails" : [ ]
}
Updated on: 30-Jul-2019
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