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Published byDennis Barber Modified over 8 years ago
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Chapter 4 Relational Algebra
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Agenda Relational Languages Relational Algebra
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Relational Languages Procedural language –Relational algebra Non-procedural language –Relational Calculus Other Languages –Transform-oriented languages –Graphical languages –Fourth-generation languages –Fifth-generation languages
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Relational Algebra Intra Relation Selection - horizontal partition –SELECT relation WHERE condition [GIVING relation] condition (relation) Projection - vertical partition –PROJECT relation OVER (attribute, attribute,...)[GIVING relation] attributes (relation)
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Union-Compatible Union - tuples in either of 2 union compatible relations –relation1 UNION relation2 [GIVING relation] –relation1 relation2 Difference - tuples in one union compatible relation, but not other —relation1 MINUS relation2 [GIVING relation] —relation1 - relation2
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Union-Compatible Intersection - tuples in both of 2 union compatible relations –relation1 INTERSECT relation2 [GIVING relation] –relation1 relation2
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Any 2 Relations Product - Cartesian product of any two relations –relation1 TIMES relation2 [GIVING relation] –relation1 relation2 Join - common domain –relation1 JOIN relation2 WHERE condition [GIVING relation] –relation1 condition relation2 Division - same pattern –relation1 divided by relation2 [GIVING relation] –relation1 / relation2
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Types of Join Equi - based on equality with 2 identical attribute columns Theta - a join based on a relational operator (=,, =,~=) Natural - equijoin with no duplicate column Outer - includes tuples without matches (left, right, full)
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Types of Outer Join Left outer join - including every tuple of the left (first) relation in the solution Right outer join - including every tuple of the right (second) relation in the solution Full outer join - including every tuple of the left (first) relation and right (second) relation in the solution
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Types of Join Semi-join: only the tuple of the left (first) relation with match –relation1 SEMIJOIN relation2 WHERE condition [GIVING relation] –relation1 lx condition relation2 Semi-theta-join Semi-natural join
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Division Examples
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Relation RRelation CRelation T1 1JJ1 1KK3 1LL 2J 2K 3L 3J 3K
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Relation RRelation CRelation T1 JonesB.S. Jensen B.S.M.S. JensenM.S.Ph.D. JensenPh.D. SmithB.S. Jensen SmithM.S. Smith RogerB.S. RogerPh.D.B.S.Jones Jensen Smith Roger
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Points To Remember Relational Languages Relational Algebra
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Assignment Review chapters 1-4, appendix c Read Chapters 5-6 Do Exercise 4.12 (only relational algebra) and 4.13 Due date: Exam date:
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