This document provides an overview and comparison of relational (SQL) databases and non-relational (NoSQL) databases. It notes that NoSQL databases provide a mechanism for storing and retrieving data with simpler designs that can scale horizontally and provide finer control over availability. NoSQL databases are increasingly used for big data and real-time applications as they can scale to handle large data volumes, have less rigid schemas than SQL databases, and do not require SQL. The document outlines some key characteristics of NoSQL databases and discusses when NoSQL may be preferable to SQL databases, such as when dealing with large amounts of data and users on the internet.

1. NoSQL Dbs.
By easydata.in
easydata - Online Training

2. Relational Databases (SQL) And Non-relational
Databases (NoSQL)
Relational Databases (SQL) Non-relational Databases (NoSQL)
Oracle MongoDB
MySQL CouchDB
SQL Server BigTable
easydata - Online Training

3. NoSQL.
• A NoSQL or Not Only SQL database provides a mechanism for storage and
retrieval of data.
• Motivations for this approach include simplicity of design, horizontal
scaling and finer control over availability.
• The data structure differs from the RDBMS, and therefore some operations
are faster in NoSQL and some in RDBMS.
• NoSQL databases are increasingly used in big data and real-time web
applications.
• NoSQL systems are also called "Not only SQL" to emphasize that they may
also support SQL-like query languages.
• Many NoSQL stores compromise consistency in favor of availability and
partition tolerance.
easydata - Online Training

4. key characteristics of NoSQL databases
• They are distributed, can scale horizontally and can handle data
volumes of the order of several terabytes or petabytes, with low
latency.
• They have less rigid schemas than a traditional RDBMS.
• They have weaker transactional guarantees.
• As suggested by the name, these databases do not support SQL.
• Many NoSQL databases model data as row with column families, key
value pairs or documents
easydata - Online Training

5. If RDBMSs are so good, Why does any one
need NoSQL databases ?
• When your application is on the internet, where you are dealing with
millions of users and data in the order of petabytes, things start to
slow down with a RDBMS.
• The basic operations with any database are read and write. Reads can
be scaled by replicating data to multiple machines and load balancing
read requests. However this does not work for writes because data
consistency needs to be maintained.
• Writes can be scaled only by partitioning the data. But this affects
read as distributed joins can be slow and hard to implement.
Additionally, to maintain ACID properties, databases need to lock data
at the cost of performance.
easydata - Online Training

6. Do not need a NoSQL store when -
• All your data fits into 1 machine and does not need to be partitioned.
• You are doing OLTP which required the ACID transaction properties
and data consistency that RDBMS is good at.
• You need ad hoc querying using a language like SQL.
• You have complicated relationships between the entities in your
applications.
• Decoupling data from application is important to you.
easydata - Online Training

7. Thank You
easydata - Online Training