How to Use Lookup in MongoDB | Join Query – Part12 of MongoDB with C# Beginner's Tutorial

This is a MongoDB C# Lookup Tutorial. Let us see how to use Lookup in MongoDB Collection from C# Application

Performs a left outer join to an unsharded collection in the same database to filter in documents from the joined collection for processing. To each input document, the lookup stage adds a new array field whose elements are the matching documents from the joined collection. The lookup stage passes these reshaped documents to the next stage.

Local Field in Lookup:
Specifies the field from the documents input to the lookup stage. Lookup performs an equality match on the local field to the foreign field from the documents of the from collection. If an input document does not contain the local field, the lookup treats the field as having a value of null for matching purposes.

Foreign Field in Lookup:
Specifies the field from the documents in the from collection. $lookup performs an equality match on the foreign field to the local field from the input documents. If a document in the from collection does not contain the foreign field, the lookup treats the value as null for matching purposes.

Playlist Link:
https://youtube.com/playlist?list=PLzewa6pjbr3JgaEaUDXWXm_bgjtQPjzFE

Tutorial Video Links:
1. How to do MongoDB Basic CRUD Operations – https://youtu.be/T2Q7KB_jdAw
2. How to do MongoDB Bulk Operations – https://youtu.be/jRhQuGeZyZA
3. How to use MongoDB Filter – https://youtu.be/EQFRVUrHIjA
4. How to use MongoDB Upsert – https://youtu.be/2QtwmVEFQKU
5. More Options in MongoDB Update – https://youtu.be/V0cJuCbZFjc
6. How to use MongoDB FindOneAndUpdate – https://youtu.be/f0XNRUI8RBk
7. How to use MongoDB BulkWrite – https://youtu.be/7CNefJC2_uU
8. More Options in MongoDB Find – https://youtu.be/ZKFlhYndXpM
9. How to Get Record By ID in MongoDB – https://youtu.be/zDLuoOJAk44
10. How to Create Index in MongoDB – https://youtu.be/js4wgmCkzek
11. How to use Batch Size in MongoDB Find – https://youtu.be/cARXNyP00Zg
12. How to Use Lookup in MongoDB – https://youtu.be/P0vDBxlFA-k

This is MongoDB and Visual Studio (C#) tutorial. All videos in this series are
developed in Visual Studio 2019 using (C#/C Sharp Language) from Microsoft. The database used is MongoDB Community Server edition.

MongoDB is a cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with optional schemas.