Database: Difference between revisions

Revision as of 03:35, 6 November 2013

Revision as of 23:46, 7 November 2013

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In recent years there was a high demand for massively distributed databases with high partition tolerance but according to the [[CAP theorem]] it is impossible for a [[Distributed computing|distributed system]] to simultaneously provide [[Consistency model|consistency]], [[availability]] and [[partition tolerance]] guarantees. A distributed system can satisfy any two of these guarantees at the same time, but not all three. For that reason many NoSQL databases are using what is called [[eventual consistency]] to provide both availability and partition tolerance guarantees with a maximum level of data consistency.

The most popular NoSQL systems include: [[MongoDB]], [[Riak]], [[Oracle NoSQL Database]], [[memcached]], [[Redis]], [[CouchDB]], [[Hazelcast]], [[Apache Cassandra]] and [[HBase]].<ref>{{cite web|url=http://db-engines.com/en/ranking |title=DB-Engines Ranking |date=January 2013 |accessdate=22 January 2013}}</ref>. Note that all are [[open-source software]] products.

A number of new relational databases continuing use of SQL but aiming for performance comparable to NoSQL are known as [[NewSQL]].

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After the database is created, initialised and populated it needs to be maintained. Various database parameters may need changing and the database may need to be tuned ([[Database tuning|tuning]]) for better performance; application's data structures may be changed or added, new related application programs may be written to add to the application's functionality, etc.

Databases are often confused with [[Spreadsheet|spreadsheetsspreadsheet]]s such as Microsoft Excel (Microsoft Access is a database management system, Excel is a spreadsheet program). Both can be used to store information, however a database is more efficient and flexible at storing large amounts of data. Below is a simple comparison of spreadsheets and databases.

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