NoSQL Dbs.

By easydata.in

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Relational Databases (SQL) And Non-relational Databases (NoSQL)

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Relational Databases (SQL) Non-relational Databases (NoSQL)

Oracle MongoDB

MySQL CouchDB

SQL Server BigTable

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.

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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

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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.

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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.

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Thank You