mongo

I will mostly be using docker to run the mongodb instance.

Documents, Collections and Databases in mongodb

  • A document is a key-value pair(like a hash table) with a unique id. Keys are strings and values. Document can have documents as values. Documents can be nested.

  • Collection is a group of documents. A database is a group of collections.

  • Database is a group of collections.

  • Each document has a unique _id.

Data types in MongoDB

  • String

  • numbers

  • boolean

  • null

  • array

  • subdocument

  • date(which is javascript Date() object)

  • ObjectId() (which is a 12 byte unique id)

  • code(which are javascript function)

Creating and connecting to the mongo container

  • To create a container with the mongodb image, I run the following command: 

    docker run -d -p 27017:27017 -v <host_dir>:/data/db/  --name test-mongo mongo:<version>

    host_dir should not be windows volume because of the permission issue.

  • Now to attach or connect to the container 

    docker exec -it test-mongo bash

  • and for security we can also use username and password. 

    docker run -d -p 27017:27017 -v <host_dir>:/data/db/  -e MONGO_INITDB_ROOT_USERNAME=<username> -e MONGO_INITDB_ROOT_PASSWORD=<password> --name test-mongo mongo:<version>

  • To connect it to mongo shell we use 

    mongosh --host localhost:<port> -u user -p pass --authenticationDatabase admin

mongosh

  • Javascript functions are present in the shell.

  • We can use mongosh --nodb to run mongo without connecting to any mongodb instance.

    • In that case we can use 

      con= new Mongo("localhost:27017")
db=con.getDB("test")

db object

  • db object is used to access the database.

  • db.insertOne(document) is used to insert a document in the collection.

  • db.insertMany(document) is used to insert multiple documents in the collection.

  • db.collection.find() is used to find the documents in the collection.(equivalent to "select * from tabel;")

    • db.collection.findOne() is used to find the first document in the collection.

    • db.collection.find(document) is used to find the documents in the collection which matches the document.

  • db.collection.updateOne(document, update) is used to update the document in the collection.

    • db.collection.updateMany(document, update) is used to update the multiple documents in the collection.

    • syntax for update is {$set: {key: value}}

  • db.collection.deleteOne(document) is used to delete the document in the collection.

    • db.collection.deleteMany(document) is used to delete the multiple documents in the collection.

  • db.collection.upsertOne(document, update) is used to update the document in the collection if it exists else it will insert the document.

    • db.collection.upsertMany(document, update) is used to update the multiple documents in the collection if it exists else it will insert the document.

  • db.collection.count() is used to count the number of documents in the collection.

  • db.collection.drop() is used to drop the collection.