# Relational Operations (Relational Algebra)

May 29th, 2015
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The first four operations are taken from mathematical set theory and are largely the same as the operations found there. The next four are new operations that apply specifically to the relational data model.

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Relational Operations (Relational Algebra)1. Union 2. Intersection 3. Difference 4. Product 5. Select 6. Project 7. Join The first four operations are taken from mathematical set theory and are largely the same as the operations found there. The next four are new operations that apply specifically to the relational data model. The "Assignment" operation is the standard computer language operation of giving a name to a value.Interestingly enough the "Data Management" text refers to restrict as a relational algebra operation. The operation "Select" does what restrict does. So for the purposes of this class the nine operations listed above are what we will recognize as relational algebra operations.Union - The union of two relations is formed by adding the tuples from one relation to those of a second relation, to create a third relation. Example:Table 1SnumNameMajor123JonesHistory158ParksMath271SmithHistoryTable 2NumberNameInterest105AndersonManagement123JonesHistoryResult of Table 1 + Table 2Snum or NumberNameMajor or Interest123JonesHistory158ParksMath271SmithHistory105AndersonManagementNote that tuple [123, Jones, History] which occurs in both Table 1 and Table 2 is not duplicated in the union. Relations must have the same number of attributes and those attributes must have like domains.The union operation in relation algebra is accomplished using the union operator ?. Union is a binary operator it oper

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