![]() ![]() Here, I’ll solve an example that will help you to understand how to join collection by their id in MongoDB. As you already know that for joining the collection we use the $lookup aggregation. In this topic, you will learn how you can join two collections by id. Read: MongoDB group by count MongoDB join two collections by id So when you have an array of fields in documents and you want to merge the collections then this way you can easily join the collections. Here we apply $lookup aggregation on member collection using the field enrollmentlist of an array and merge the two collections with foreignField name and that displays the below output. Now, we apply aggregation operation and join documents of the members’ collection with classes collection. Here, these are some documents we inserted into the members’ collection. ![]() This is the simple syntax or query that is used to join two collections. In this, you have to specify which collection you want to join with the current collection and select the field that matches in both the collection. In MongoDB, we can combine data of multiple collections into one through the $lookup aggregation stage. Read: MongoDB group by multiple fields MongoDB join two collections query If documents come from the “joined” collection, the $lookup (aggregation) function will return the documents in the form of a sub-array of the target original collection. The $lookup(aggregation) is a stage that makes a left outer join with another collection and assists to filters the documents from joined documents. In MongoDB, the $lookup (aggregation) function allows us to join the documents on collections that reside in the same database. MongoDB join two collections using python What is used for joining the collection in MongoDB?
0 Comments
Leave a Reply. |