Document databases are a class of non-relational databases (NoSQL databases). Document databases store related data in a document format. They are used to design, query, and store the data in a document format (JSON document, XML, YAML, or binary formats such as BSON and PDF). The software is used for storing, retrieving, and managing document-oriented information also known as semi-structured data. Document databases software, also known as document-oriented databases software, is a subclass of key-value stores, which is a NoSQL database concept. In a key-value store or key-value database, data is managed (stored, received) by using associative arrays. This type of data structure is called a “dictionary”. Dictionaries are a collection of objects, and objects are the central data storage repository that store different fields that contain the data. Some of the key examples include MongoDB, Amazon DynamoDB, Google Cloud Firestore, Couchbase Server, Apache CouchDB, among several others. Many of these databases such as MongoDB and Couchbase server are open source in nature.
To call the data when required, a key is used, which acts as the unique identifier for the record within the entire database. When talking about document databases, it’s important to identify what exactly is a “document”. A document stores or encodes all the data in a standard format. These formats include JSON, XML, YAML, and others.
Document databases differ greatly from traditional relational SQL databases. The major cause of difference between the two types of databases is that relational databases store data models as a relation—tables, rows, and an object could be a part of numerous tables. However, document databases store all the related information of an object within a single instance of the database, and each object can be stored uniquely. Document databases do not have any restrictions as relational databases do.
CRUD operation
The core operations for document databases are abbreviated as CRUD—create, retrieve, update, and delete. These are the four basic operations that all document databases support.
What is a key?
As stated earlier, a key acts as a unique identifier that is representative of the document. It is used to retrieve the data from the document database. There is usually an index of keys available, which makes it easier for the user to refer to and call back the data represented by that particular key. In case a user needs to add or delete a document within the document database, a key can be used for the same.
Data retrieval
Although a key-to-document method is enough for data retrieval, the document database offers an API that users can use to query data based on content. The set of query language or query APIs vary significantly between different data model implementations. In this, document databases make use of the metadata of the content to classify the content and differentiate it from one another.
Data organization
There are several ways to arrange documents within document databases software. A document can exist as single or multiple collections.
Hierarchy: Documents are grouped in a tree-like structure and have a typical path.
Collections: Group of documents within the software.
Data tags: Documents or additional data located outside the content.
Why use document databases?
Since the data is stored in a format that is very close to the application development code used by developers, there is much less translation required for the data to be used by an application. These types of databases give developers the freedom and the flexibility to rework various documents in the format suited for that application. In turn, their application needs to change over time, the document database can also be modeled in the same data format as required by the application.
When can a user opt for document databases?
Document databases software is used to store large volumes of data in a key-value, making it easy for the user to access the data. Considering the significant amount of data to be processed, some of the key uses of the software include content management, user profiles for a company, catalogs, and several other documents.
