I’ll introduce how to connect to another database and execute queries in MongoDB.

Prerequisites

Let’s assume we’re managing collections separately across two DB servers.

Database 1

• Host: mongodb1
• Port: 27017
• DB: myDb

Database 2

• Host: mongodb2
• Port: 27017
• DB: myDb

How to Create a Connection to Another DB

When you want to handle collections from another DB while executing queries in mongo shell, you can create a connection to that DB.

$ mongo mongodb1/myDb
mongodb1> db2 = connect("mongodb2:27017/myDb")
connecting to: mongodb2:27017/myDb
myDb

// You can now handle data from somecollections saved in myDb on mongodb2 server
mongodb1> db2.somecollections.findOne()

When there was only one DB server, I didn’t need to worry about this, but with multiple servers, knowing tips for handling connections to different DB servers lets you keep executing queries from mongo shell as usual.

Reference Information

• connect() — MongoDB Manual 3.4
• Various Mongo shell tricks - Qiita

That’s all from the Gemba.