CODEWITHSUNDEEP
mongodbjoin
sathyam puttala
sathyam puttala

Reputation: 11

How to merge two collections in mongodb

I have two collections called Company_Details and Company_Ranks...Comp_ID is common in two collections. How do I merge these two collections to get complete details of a company.

Please help me

Thanks Satyam

Upvotes: 1

Views: 809

Answers (3)

AkAk47
AkAk47

Reputation: 291

With MongoDB Version 3.2 and higher we got now the $lookup Command, which is the "same" as a Join in a RDBMS.
With that you can easy Query between your 2 Collections and get the Information you want.
For further Details Checkt out the Documentation
https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/

Upvotes: 0

Dev
Dev

Reputation: 13753

If querying is your motive and you don't want to change your schema. Then, try Apache Drill which allows you to query with SQLs. Then perform the full join, inner join, etc whatever you want. You can check for drill with MongoDB.

Upvotes: 0

TechWisdom
TechWisdom

Reputation: 4285

To make long story short, you either do that on client-side or consider the benefits of embedding those documents.

MongoDB does not support joins, as opposed to relational databases. This is both a pro and a con. It has helped MongoDB's developers to focus on scalability which is much harder to implement when you have joins and transactions.

You can follow the DBRef specification. Lots of drivers support DBRef and do the composition seamlessly for you. You can even do that manually. But most importantly, you can take advantage of embedding documents.

Embedding documents in MongoDB is a unique ability over relational databases. Meaning, you can create one collection consisting of compound documents. You'll enjoy atomicity, as there is no "partial success", and data locality: spinning disks are better in accessing data in sequence.

Upvotes: 1

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