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MongoDB Aggregate JSON array field for the matching field of other collection?
For this, create two collections and add some document. After that, use $lookup for match. Let us create a collection with documents −
> db.demo101.insertOne(
... { "_id" : "1", "Details" : [ { "PId" : "200" }, { "PId" : "201" }, { "PId" : "201" } ] }
... )
{ "acknowledged" : true, "insertedId" : "1" }Display all documents from a collection with the help of find() method −
> db.demo101.find();
This will produce the following output −
{ "_id" : "1", "Details" : [ { "PId" : "200" }, { "PId" : "201" }, { "PId" : "201" } ] }Following is the query to create second collection with some documents −
> db.demo102.insertOne(
... { "_id" : "201", "CustEmailId" : "Carol@gmail.com" }
... );
{ "acknowledged" : true, "insertedId" : "201" }Display all documents from a collection with the help of find() method −
> db.demo102.find();
This will produce the following output −
{ "_id" : "200", "CustEmailId" : "John@gmail.com" }
{ "_id" : "201", "CustEmailId" : "Carol@gmail.com" }Following is the query to aggregate JSON array field for the matching field of other collection −
> db.demo101.aggregate(
... [
... {$unwind:"$Details"},
... {$lookup : {from : "demo102", "localField":"Details.PId", "foreignField":"_id", as :"out"}},
... {$project : {"_id":1, "Details.PId":{$arrayElemAt:["$out.CustEmailId",0]}}},
... {$group:{_id:"$_id", Details : {$push : "$Details"}}}
... ]
... ).pretty()This will produce the following output −
{
"_id" : "1",
"Details" : [
{
"PId" : "John@gmail.com"
},
{
"PId" : "Carol@gmail.com"
},
{
"PId" : "Carol@gmail.com"
}
]
}
Updated on: 30-Mar-2020
455 Views
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