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MongoDB query to unwind two arrays
To unwind, means to deconstruct an array field from the input documents to output a document for each element.
To unwind arrays, use $unwind in MongoDB aggregation. Let us first create a collection with documents −
> db.demo387.insertOne(
... {
...
... "Name" : "101",
... "Details1" : [
... {Value:100, Value1:50, Value2:40},
... {Value:200},
... {Value:300}
... ],
... "Details" : [
... {Value:100, Value1:30, Value2:26},
... {Value:200},
... {Value:300}
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5d197022064be7ab44e7f8")
}Display all documents from a collection with the help of find() method −
> db.demo387.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5e5d197022064be7ab44e7f8"),
"Name" : "101",
"Details1" : [
{
"Value" : 100,
"Value1" : 50,
"Value2" : 40
},
{
"Value" : 200
},
{
"Value" : 300
}
],
"Details" : [
{
"Value" : 100,
"Value1" : 30,
"Value2" : 26
},
{
"Value" : 200
},
{
"Value" : 300
}
]
}Following is the query to aggregate document with more than 1 array −
> db.demo387.aggregate([
... { "$unwind": "$Details1" },
... { "$unwind": "$Details" },
... { "$match": { "$expr":
... { "$eq": ["$Details1.Value", "$Details.Value"] }
... }}
... ])This will produce the following output −
{ "_id" : ObjectId("5e5d197022064be7ab44e7f8"), "Name" : "101", "Details1" : { "Value" : 100, "Value1" : 50, "Value2" : 40 }, "Details" : { "Value" : 100, "Value1" : 30, "Value2" : 26 } }
{ "_id" : ObjectId("5e5d197022064be7ab44e7f8"), "Name" : "101", "Details1" : { "Value" : 200 }, "Details" : { "Value" : 200 } }
{ "_id" : ObjectId("5e5d197022064be7ab44e7f8"), "Name" : "101", "Details1" : { "Value" : 300 }, "Details" : { "Value" : 300 } }
Updated on: 02-Apr-2020
429 Views
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