NoSql vs Relational database

Question

Recently NoSQL has gained immense popularity    What are the advantages of NoSQL over traditional RDBMS

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If you need to process huge amount of data with high performance   OR   If data model is not predetermined   then   NoSQL database is a better choice

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Not all data is relational   For those situations  NoSQL can be helpful   With that said  NoSQL stands for  Not Only SQL    It s not intended to knock SQL or supplant it     SQL has several very big advantages     Strong mathematical basis  Declarative syntax  A well-known language in Structured Query Language  SQL     Those haven t gone away   It s a mistake to think about this as an either or argument   NoSQL is an alternative that people need to consider when it fits  that s all   Documents can be stored in non-relational databases  like CouchDB   Maybe reading this will help

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From mongodb com      NoSQL databases differ from older  relational technology in four main areas       Data models  A NoSQL database lets you build an application without having to define the schema first unlike relational databases which make you define your schema before you can add any data to the system  No predefined schema makes NoSQL databases much easier to update as your data and requirements change       Data structure  Relational databases were built in an era where data was fairly structured and clearly defined by their relationships  NoSQL databases are designed to handle unstructured data  e g   texts  social media posts  video  email  which makes up much of the data that exists today       Scaling  It   s much cheaper to scale a NoSQL database than a relational database because you can add capacity by scaling out over cheap  commodity servers  Relational databases  on the other hand  require a single server to host your entire database  To scale  you need to buy a bigger  more expensive server       Development model  NoSQL databases are open source whereas relational databases typically are closed source with licensing fees baked into the use of their software  With NoSQL  you can get started on a project without any heavy investments in software fees upfront

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NOSQL has no special advantages over the relational database model  NOSQL does address certain limitations of current SQL DBMSs but it doesn t imply any fundamentally new capabilities over previous data models   NOSQL means only no SQL  or  not only SQL   but that doesn t mean the same as no relational  A relational database in principle would make a very good NOSQL solution - it s just that none of the current set of NOSQL products uses the relational model

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RDBMS focus more on relationship and NoSQL focus more on storage    You can consider using NoSQL when your RDBMS reaches bottlenecks  NoSQL makes RDBMS more flexible

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The history seem to look like this   Google needs a storage layer for their inverted search index  They figure a traditional RDBMS is not going to cut it  So they implement a NoSQL data store  BigTable on top of their GFS file system  The major part is that thousands of cheap commodity hardware machines provides the speed and the redundancy   Everyone else realizes what Google just did   Brewers CAP theorem is proven  All RDBMS systems of use are CA systems  People begin playing with CP and AP systems as well  K V stores are vastly simpler  so they are the primary vehicle for the research   Software-as-a-service systems in general do not provide an SQL-like store  Hence  people get more interested in the NoSQL type stores    I think much of the take-off can be related to this history  Scaling Google took some new ideas at Google and everyone else follows suit because this is the only solution they know to the scaling problem right now  Hence  you are willing to rework everything around the distributed database idea of Google because it is the only way to scale beyond a certain size  C - Consistency  A - Availability  P - Partition tolerance K V - Key Value

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The biggest advantage of NoSQL over RDBMS is Scalability  NoSQL databases can easily scale-out to many nodes  but for RDBMS it is very hard  Scalability not only gives you more storage space but also much higher performance since many hosts work at the same time

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NoSQL is better than RDBMS because of the following reasons properities of NoSQL   It supports semi-structured data and volatile data It does not have schema Read Write throughput is very high Horizontal scalability can be achieved easily  Will support Bigdata in volumes of Terra Bytes  amp  Peta Bytes Provides good support for Analytic tools on top of Bigdata Can be hosted in cheaper hardware machines In-memory caching option is available to increase the performance of queries Faster development life cycles for developers   EDIT    To answer  why RDBMS cannot scale   please take a look at RDBMS Overheads pdf written by Stavros Harizopoulos Daniel J  Abadi Samuel Madden and  Michael Stonebraker  RDBMS s have challenges in handling huge data volumes of Terabytes  amp  Peta bytes  Even if you have Redundant Array of Independent Inexpensive Disks  RAID   amp  data shredding  it does not scale well for huge volume of data  You require very expensive hardware   Logging  Assembling log records and tracking down all changes in database structures slows performance  Logging may not be necessary if recoverability is not a requirement or if recoverability is provided through other means  e g   other sites on the network    Locking  Traditional two-phase locking poses a sizeable overhead since all accesses to database structures are governed by a separate entity  the Lock Manager   Latching  In a multi-threaded database  many data structures have to be latched before they can be accessed  Removing this feature and going to a single-threaded approach has a noticeable performance impact   Buffer management  A main memory database system does not need to access pages through a buffer pool  eliminating a level of indirection on every record access   This does not mean that we have to use NoSQL over SQL    Still  RDBMS is better than NoSQL for the following reasons properties of RDBMS   Transactions with ACID properties - Atomicity  Consistency  Isolation  amp  Durability Adherence to Strong Schema of data being written read Real time query management   in case of data size  lt  10 Tera bytes   Execution of complex queries involving join  amp  group by clauses   We have to use RDBMS  SQL  and NoSQL  Not only SQL  depending on the business case  amp  requirements

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Just adding to all the information given above  NoSql Advantages   1  NoSQL is good if you want to be production ready fast due to its support for schema-less and object oriented architecture   2  NoSql db s are eventually consistent which in simple language means they will not provide any lock on the data documents  as in case of RDBMS and what does it mean is latest snapshot of data is always available and thus increase the latency of your application   3  It uses MVCC  Multi view concurrency control  strategy for maintaining and creating snapshot of data documents    4  If you want to have indexed data you can create view which will automatically index the data by the view definition you provide   NoSql Disadvantages   1  Its definitely not suitable for big heavy transactional applications as it is eventually consistent and does not support ACID properties   2  Also it creates multiple snapshots  revisions  of your data  documents  as it uses MVCC methodology for concurrency control  as a result of which space get consumed faster than before which makes compaction and hence reindexing more frequent and it will slow down your application response as the data and transaction in your application grows  To counter that you can horizontally scale the nodes but then again it will be higher cost as compare sql database

[database] NoSql vs Relational database

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