get id which exists in collection a but not in collection b mongo

Upvote answer :-) answered on August 9, 2022 Popularity 3/10 Helpfulness 2/10

answer get id which exists in collection a but not in collection b mongo

get id which exists in collection a but not in collection b mongo

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//MONGO
//get ids that appear in collection1 but not in collection2

db.collection1.aggregate(
[
	{
		$lookup: 
			{
				from: "collection2",
				localField: "id",
				foreignField: "id",
				as: "matched_docs"
			}
	},
	{
		$match: 
		{
			"matched_docs": { $eq: [] }
		}
	},
	{$project:
		{
         id: 1
    	}
    }
]);

Popularity 3/10 Helpfulness 2/10 Language javascript

Source: Grepper

Tags: exists get ids javascript mongodb

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Contributed on Aug 09 2022

Upvote answer :-)

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get id which exists in collection a but not in collection b mongo

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