Since data is stored in cells grouped in columns so all read-write is done using columns, not rows. In this type of database, the focus is on columns rather than rows as data is stored in columns instead of rows which is the case with most relational databases.These types of databases are used extensively especially in big data analysis. The examples of databases using the above data model are MongoDB and Couchbase.The difference between conventional databases and document-based databases is that data here is not stored in tables like conventional databases but are stored in documents.The below example shows a document that can be stored in a document database but with a different encoding.The difference between a document and Key value pair is that in document type storage is that in this type some kind of encoding is provided while storing the data in documents, It can be XML encoding or JSON encoding.So this model is not completely unstructured but it is a kind of Semi-structured data. In this type of database, the record and its associated data are stored in a single document.Examples of databases applying Key-Value pairs are Oracle NoSQL database and Redis. We can even store complete URLs as the URL name can be the key and the actual URL as value. These are extensively used in big data analytics. The key-value database model can be useful for storing data on Ecommerce like product categories, product details, etc.You can also specify the data type of the value here. The value in the key-value pair can be anything from a String to an image. The size of the key is important here as a long key can cause performance issues whereas a too short a key can cause readability issues.

For example in Redis, the maximum size for Key is 512mb. The rules set for what the key can be the length for the size of the key depends on the database to the database. The key in the key-value pair must be unique. As the name suggests the Key-value store simply uses the key value to store data in the database.They are as follows and we will discuss them one by one. In general, there are four different types of data models in NoSQL.

Nosql database modeling tools