MongoDB

MongoDB is an unstructured database. It stores data in the form of documents. MongoDB is able to handle huge volumes of data very efficiently and is the most widely used NoSQL database as it offers rich query language and flexible and fast access to data.

Let’s take a moment to understand the architecture of a MongoDB database.

The Architecture of a MongoDB Database

The information in MongoDB is stored in documents. Here, a document is analogous to rows in structured databases.

• Each document is a collection of key-value pairs
• Each key-value pair is called a field
• Every document has an _id  field, which uniquely identifies the documents
• A document may also contain nested documents
• Documents may have a varying number of fields (they can be blank as well)

These documents are stored in a collection. A collection is literally a collection of documents in MongoDB. This is analogous to tables in traditional databases.

Unlike traditional databases, the data is generally stored in a single collection in MongoDB, so there is no concept of joins (except $lookup operator, which performs left-outer-join like operation). MongoDB has the nested document instead.