Document-oriented database
A document-oriented database is a database in which documents form the basic unit for storing the data. The most widespread database system with a document-oriented database is HCL Notes (before 2019 IBM or Lotus Notes). Since they do not follow a relational approach and do without SQL , document-oriented databases are among the NoSQL databases.
While a relational database consists of database tables that are subject to a fixed database schema , a document-oriented database contains individual documents with a unique identifier . A document corresponds to one line in a database table. These documents can now be structured files with a standard file format (such as a word processing program file ), but binary large objects are also possible that are not further structured in terms of database access (such as a video film in mpeg format). Since the documents are schema-free, a database can contain different types of documents. By assigning the documents to a unique key, document -oriented databases are very similar to key-value databases . While key-value databases do not consider the value assigned to the key any further, document-oriented databases offer options for evaluating documents directly or for changing their content.
In current database systems such as CouchDB and MongoDB , these documents contain semi-structured data such as JSON , YAML or XML (see also XML database ). This enables the storage of complex data structures in the database and their query based on certain properties. In contrast to relational databases, these structures do not have to be mapped onto tables, which makes the processes of saving and reading less complex. However, the lack of options for normalization can result in redundancies in the data and the application that is supposed to use the data becomes more complex, as it may have to ensure that the data is consistent itself.
Further document-oriented database management systems are:
In addition, relational database systems such as PostgreSQL and MySQL offer options for storing semi-structured data in tables and evaluating them in a similar way to a document-oriented database. This enables the relational and the document-oriented approach to be combined.
literature
- Wassilios Kazakos, Andreas Schmidt, Peter Tomczyk, D. Gündisch, T. Marz, Guido Moerkotte, A. Valikov: Databases and XML: Concepts, Applications, Systems (Xpert.press) . Springer, 2002, ISBN 978-3-540-41956-3 .
- Peter Gluchowski, Roland Gabriel, Carsten Dittmar: Management Support Systems and Business Intelligence: Computer-aided information systems for specialists and executives . Springer, 2008, ISBN 978-3-540-23543-9 .
Individual evidence
- ^ Rod Stephens: Beginning Database Design Solutions . Wiley-India, New Delhi 2008, p. 44. ISBN 81-265-1917-7 .
- ↑ http://wi-wiki.de/doku.php?id=bigdata:dokumentdb
- ↑ https://entwickler.de/online/datenbanken/mongodb-erverbindreich-ein-dokumentenorientierter-datenbanksystem-einfuehren-115079.html
- ↑ https://www.postgresql.org/docs/10/datatype-json.html
- ↑ https://dev.mysql.com/doc/refman/8.0/en/json.html