Abstract
No discussion of relational databases would be complete without a reference to Edgar Codd’s 1970 paper “A Relational Model of Data for Large Shared Data Banks”. This was a mathematical description of what we now call Relational databases and operations to manipulate them. This is called relational algebra where data could be organised into relations (tables) consisting of tuples (records), each with consistent attributes. The tables could be linked or joined by using relationships based on a unique identifier of each of the records, the primary key. As well as describing the structure of the data, a method called normalisation was developed to assist with the design of relational databases. An alternative approach to developing a logical design of a database is to identify entities in the system and then map the relationships between them Codd also described a number of operations which could be performed on it. These included selection, projection and joins between tables. Selection and joins are common terminology in databases, but projection defines conditions on the data you want to retrieve, for example people with an age greater than 18. Ultimately these operations were formalised into a structured query language or SQL. This was released in 1979 by what was to become Oracle Corporation.
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References
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Further Reading
Chen P (2006) Suggested research directions for a new frontier: active conceptual modeling. In: Conceptual modeling—ER 2006. Lecture notes in computer science, vol 4215. Springer, Berlin/Heidelberg, pp 1–4
Microsoft (2013) Microsoft SQL server library. Available on line at http://msdn.microsoft.com/en-us/library/bb545450.aspx. Accessed 22/04/2013
Oracle® (2010) Database SQL language reference 11g release 1 (11.1). Available on line at http://docs.oracle.com/cd/B28359_01/server.111/b28286/toc.htm#BEGIN. Accessed 22/04/2013
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Lake, P., Crowther, P. (2013). Relational Databases. In: Concise Guide to Databases. Undergraduate Topics in Computer Science. Springer, London. https://doi.org/10.1007/978-1-4471-5601-7_4
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DOI: https://doi.org/10.1007/978-1-4471-5601-7_4
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