Web18 jun. 2024 · Since the data type of user._id(ObjectId) and post.user_id(String) are not the same you can not join those fields using $lookup. You have to make sure they are the … Web30 okt. 2015 · The .aggregate() method always returns Objects no matter what you do and that cannot change. For your purpose you are probably better off using .distinct() instead, …
$lookup (aggregation) — MongoDB Manual
Web23 mei 2024 · Get values as array of elements after $lookup. For MongoDB, when using $lookup to query more than one collection, is it possible to get a values-only list for a … Web1 dag geleden · Teams. Q&A for work. Connect and share knowledge within a single location that is structured and easy to search. Learn more about Teams somerville ma chamber of commerce
mongodb - $lookup mongodb4.0中对象的多级嵌套数组 - $lookup …
WebI have a collection in mongo which has array field. When I query that collection I want to return documents whose elements in the array field represent a subset of the array I'm comparing with. So all array elements in the document that satisfies the condition should also be present in the array I'm comparing with but that array can have additional … Web5 aug. 2024 · It's returning an empty array instead of the object I'm searching for. What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version. Node: 12.6.0 Mongoose: 5.6.0. I'm trying to make a query on an aggregated field (a field from another collection). If I don't match anything, one of the documents is ... Web25 mei 2024 · In a MongoDB database, data is stored in collections and a collection has documents. A document has fields and values, like in a JSON. The field types include scalar types ( string, number, date, etc.) and composite types ( arrays and objects ). In this article we will look at an example of using the array field type. small chair for shower