In our previous post, I already wrote about MongoDB, a NoSQL database server that today is growing really fast. Here you have seen how to install it and how to start it. Now, let’s see how to work with MongoDB.
On a MS-DOS console, execute mongo:
Iniciando MongoDB
If you want to know the databases you have on the server, just write show dbs.
mongodb Show dbs
The MongoDb console is also a JavaScript console, and because of this, you should be careful with the names you use becasue of lower and upper case. If we try SHOW dbs written of several different forms, all of them give us errors (excepto if we write it on lowercase):
MongoDB & Javascript
To use a database, just write the command use manejandodatos, as you do when working with MySQL:
MongoDB – use manejandodatos
Let’s check that MongoDB console is a Javascript console as well, just writting a simple math operation:
MongoDB & Javascript
Now, let’s create our first documents:
dato1 = { nombre: 'Juan' };
dato2 = { edad: 34 };
And store it on the collection amigos (friends) con save:
db.amigos.save(dato1);
db.amigos.save(dato2);
MongoDB – Guardando datos
Let’s show the documents of our friends “amigos“. The SQL sentence should be SELECT * FROM amigos , and the MongoDb sentence is db.amigos.find():
MongoDB – Mostrando documentos
The SQL insert INSERT amigos(fields) VALUES (value) of SQL is transformed to db.amigos.save({ field: value })
MongoDB
Now that we have 3 friends, it’s time to update some information. The update sentence UPDATE amigos SET field = value WHERE condition is equal to db.amigos.update( { condition } , { field: value } )
MongoDB – Actualizando documentos
In the previous image we have modified the information Nombre: Luis by Edad: 32. We hava modified the identifier and the key, even if the types of data are different.
In order to update a document with new properties (or more than one document), you have to include $set, or $unset to remove. Let’s inset a new name without name:
MongoDB – Actualizando documentos
If you want to cound the number of documents, the SQL sentence you need is SELECT COUNT(*) FROM amigos, but in MongoDB you’ll write db.amigos.count():
MongoDB – Agregados
To end with, the SQL sentence DELETE FROM tabla is db.amigos.remove() in MongoDB:
MongoDB – Remove
If you want to re-start a collection instead of removing all documents (in MySQL you’ll use the TRUNCATE sentence), in MongoDB you can do exactly the same with the sentence db.amigos.drop().
The difference between remove and drop is that when using remove the collecion remove one document for operation, so, removing several document requires reveral operations, while drops deletes all document on one operation. For small datasets you won’t find much differences. With large datasets, the results is totally different!
I hope you enjoy playing with MongoDB as much as I did!