El tutorial básico de MongoDB

MongoDB es una base de datos, la parte de la aplicación responsable de almacenar y recuperar información.

MongoDB es una base de datos NoSQL. Bajo laNoSQLParaguas ponemos todas aquellas bases de datos que no utilizan el lenguaje SQL para consultar los datos.

Características clave de MongoDB

MongoDB es una base de datos muy compatible con JavaScript. Expone una API de JavaScript que podemos usar para crear bases de datos y colecciones de objetos (llamadodocumentos).

Essin esquema, lo que significa que no es necesario predefinir una estructura para los datos antes de almacenarlos.

En MongoDB puede almacenar cualquier objeto sin tener que preocuparse por los campos particulares que componen este objeto y cómo almacenarlos. Le dice a MongoDB que almacene ese objeto.

Los datos se almacenan en un formato similar a JSON, pero mejorado para permitir almacenar más que solo tipos de datos básicos.

Instalación

Sigamos e instalemos MongoDB. Puede usar uno de los muchos proveedores en la nube que ofrecen acceso a una instancia de MongoDB, pero para aprender, lo instalaremos nosotros mismos.

Utilizo una Mac, por lo que las instrucciones de instalación de este tutorial se refieren a ese sistema operativo.

Abra la terminal y ejecute:

brew tap mongodb/brew
brew install mongodb-community

Eso es.

Las instrucciones no fueron demasiado largas ni complicadas, suponiendo que sepa cómo usar el terminal ycómo instalar Homebrew.

La instalación nos dice esto:

To have launchd start mongodb now and restart at login:
  brew services start mongodb-community
Or, if you don't want/need a background service you can just run:
  mongod --config /usr/local/etc/mongod.conf
You can choose to either launch MongoDB once and have it running forever as a background service in your computer (the thing I prefer), or you can run it just when you need it, by running the latter command.


The default configuration for MongoDB is this:


systemLog:
  destination: file
  path: /usr/local/var/log/mongodb/mongo.log
  logAppend: true
storage:
  dbPath: /usr/local/var/mongodb
net:
  bindIp: 127.0.0.1
Logs are stored in /usr/local/var/log/mongodb/mongo.log and the database is stored in /usr/local/var/mongodb.


By default there is no access control, anyone can read and write to the database.


The Mongo Shell


The best way to experiment with MongoDB and starting to interact with it is by running the mongo program, which starts the MongoDB shell.




You can now enter any command that Mongo understands.


Create a database


When you start, Mongo creates a database called test. Run db in the shell to tell you the name of the active database




To change the database, just write use newname and the newname database will be instantly created and the shell switches to using that.




Use show databases to list the available databases:




As you can see, the something database is not listed, just because there is no collection yet in it. Let’s create one.


Collections


In MongoDB, a collection is the equivalent of a SQL database table.


You create a collection on the current database by using the db.createCollection() command. The first argument is the database name, and you can pass an options object as a second parameter.




Once you do so, show databases will list the new database, and show collections will list the collection.




You can also create a new collection by using it as a property of the db object, and calling insert() to add an object to the collection:


db.dogs.insert({ name: 'Roger' })





Listing objects in a collection


To show the objects added to a collection, use the find() method:




As you can see there is an additional _id property for the record we added. That’s automatically generated for us by MongoDB.


Now, add more dogs:


db.dogs.insert({ name: 'Buck' })
db.dogs.insert({ name: 'Togo' })
db.dogs.insert({ name: 'Balto' })



Calling db.dogs.find() will give us all the entries, while we can pass a parameter to filter and retrieve a specific entry, for example with db.dogs.find({name: 'Roger'}):




The find() method returns a cursor you need to iterate on.


There is another method which is handy when you know you’ll only get one record, which is findOne(), and it’s used in the same way. If multiple records match a query, it will just return the first one.




Updating records


To update a record you can use the update() method on a collection:




Removing records


You can remove a record calling the remove() method on a collection, passing an object to help identify it:




To remove all the entries from a collection, pass an empty object:


db.dogs.remove({})


  

  




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