The Little MongoDB Book
Learn about MongoDB a document-oriented NoSQL database.
We begin our journey by getting to know the basic mechanics of working with MongoDB. Obviously this is core to understanding MongoDB, but it should also help us answer higher-level questions about where MongoDB fits.
To get started, there are six simple concepts we need to understand.
1. MongoDB has the same concept of a database with which you are likely already familiar. Within a MongoDB instance you can have zero or more databases, each acting as high-level containers for everything else.
2. A database can have zero or more collections. A collection shares enough in common with a traditional table that you can safely think of the two as the same thing.
3. Collections are made up of zero or more documents. Again, a document can safely be thought of as a row.
4. A document is made up of one or more fields, which you can probably guess are a lot like columns.
5. Indexes in MongoDB function mostly like their RDBMS counterparts.
6. Cursors are different than the other five concepts but they are important enough, and often overlooked, that I think they are worthy of their own discussion. The important thing to understand about cursors is that when you ask MongoDB for data, it returns a pointer to the result set called a cursor, which we can do things to, such as counting or skipping ahead, before actually pulling down data.