Relational Data Manipulation.
Written by VR Saturday, 02 April 2011 19:07
The manipulation part of the relational model consist of a set of operators known collectively as the relational algebra together with a relational assignment operator which assigns the value of some arbitrary expression of the algebra to another relation. Each operator of the relational algebra takes either one or two relations as its input and produces a new relation as its output.Codd originally defined eight such operators two groups of four each(1) the traditional set operations union,intersection,difference and Cartesian product and (2) the special relational operation restrict project, join and divide.
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