Chapter 4 Relational Algebra

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Chapter 4Relational Algebra

• Relational Languages
• Relational Algebra

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Relational Languages

• Procedural language
• Relational algebra
• Non-procedural language
• Relational Calculus (pp.101- 107)

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Relational AlgebraIntra 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
• 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
  (,lt,gt,lt,gt,)
• Natural equijoin with no duplicate column
• Outer includes tuples without matches (left,
  right, full)

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Types of Join

• Semi-join
• relation1 SEMIJOIN relation2 WHERE condition
  GIVING relation
• relation1 lxcondition relation2
• Semi-theta-join
• Semi-natural join

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Assignment

• Review chapters 1-4
• Read Chapters 6-5
• Do Exercise 4.12
• Due date