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Is it possible to achieve a slice chain in MongoDB?
Yes, you can achieve this using aggregate framework. Let us first create a collection with documents −
> db.sliceOfSliceDemo.insertOne(
... {
... "Name": "John",
... "Details": [["First 1:1", "First 1:2"],["second 2:1","Second 2:2"]]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ccf3fcfdceb9a92e6aa195a")
}Following is the query to display all documents from a collection with the help of find() method −
> db.sliceOfSliceDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5ccf3fcfdceb9a92e6aa195a"),
"Name" : "John",
"Details" : [
[
"First 1:1",
"First 1:2"
],
[
"second 2:1",
"Second 2:2"
]
]
}Following is the query to get a slice of a slice i.e. achieve a slice chain in MongoDB −
> db.sliceOfSliceDemo.aggregate([ {$match:{"Name":"John"}},
{$unwind:"$Details"},
{$unwind:"$Details"},
{$group:{"_id":"$Name","Details":{$last:"$Details"}}},
{$project:{"Name":"$_id","Details":1}} ]);This will produce the following output −
{ "_id" : "John", "Details" : "Second 2:2", "Name" : "John" }
Updated on: 30-Jul-2019
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