We matched the name field and the contact_name field of these two collections. It is important to note that the name field in the address collection has the same values as the contact_name field in the userInfo collection.Īpplying the $lookup function, we find an equality match as follows: ([ The userInfo collection was populated with some documents. Now let’s add a few documents to another collection: db.userInfo.insertMany( The following example creates a sample dataset and inserts some documents to perform MongoDB Join two collections: db.address.insertMany(Ī few documents were inserted into the address collection. The data that was joined by the query will be the first element in the grades array. To join two collections, we use the $lookup operator, whose syntax is defined below: In MongoDB’s JOIN operation, the goal is to connect one set of data to another set of data. If documents are part of a “joined” collection, the $lookup (Aggregation) function will return documents in the form of a subarray of the original collection. $lookup(Aggregation) creates an outer left join with another collection and helps to filter data from merged data. We can join documents on collections in MongoDB by using the $lookup (Aggregation) function. To resolve this problem, we introduce the JOIN concept, which facilitates the relationship between the data. MongoDB has some issues with linking data from one collection to another unless you use simple Script Query functions. MongoDB is a straightforward and simple-to-configure database that provides high performance, automatic scalability, and high availability. Furthermore, it is distributed under the Server Side Public License (SSPL), which supports a novel mechanism for storing and retrieving large amounts of data. This enables it to store various types of data. MongoDB, which was founded in 2009, employs the Document-Oriented Database Model to organize data into documents and collections rather than tables. MongoDB is a non-relational Database Management System that is Open Source and Cross-Platform.
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