lecture 7.pptx - DATABASE MANAGEMENT SYSTEMS 1 Lecture 7 BRIEF RECAP Relational Model Relational keys Primary key Foreign key Referential Actions on

lecture 7.pptx - DATABASE MANAGEMENT SYSTEMS 1 Lecture 7...

This preview shows page 1 - 10 out of 31 pages.

DATABASE MANAGEMENT SYSTEMS Lecture # 7 1
Image of page 1
BRIEF RECAP Relational Model Relational keys Primary key Foreign key Referential Actions on Foreign Keys Restrict Cascade Nullify Default 2
Image of page 2
RELATIONAL ALGEBRA 3
Image of page 3
INTRODUCTION Relational algebra and relational calculus are formal languages associated with the relational model. Informally, relational algebra is a (high-level) procedural language and relational calculus a non-procedural language. However, formally both are equivalent to one another. 4
Image of page 4
RELATIONAL ALGEBRA Relational algebra operations work on one or more relations to define another relation without changing the original relations. Both operands and results are relations, so output from one operation can become input to another operation. Allows expressions to be nested, just as in arithmetic. This property is called closure . 5
Image of page 5
RELATIONAL ALGEBRA Five basic operations in relational algebra: Selection, Projection, Cartesian product, Union, and Set Difference. These perform most of the data retrieval operations needed. Also have Join, Intersection, and Division operations, which can be expressed in terms of 5 basic operations. 6
Image of page 6
7 RELATIONAL ALGEBRA OPERATIONS
Image of page 7
- RELATIONAL ALGEBRA OPERATIONS Select Project Rename Union Difference Intersection Assignment Cartesian Product Join Outer Union Composition of Operators Aggregate Functions Null Values 8
Image of page 8
SELECTION (OR RESTRICTION) predicate (R) Works on a single relation R and defines a relation that contains only those tuples (rows) of R that satisfy the specified condition ( predicate ).
Image of page 9
Image of page 10

You've reached the end of your free preview.

Want to read all 31 pages?

  • Fall '19
  • ali

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Ask Expert Tutors You can ask You can ask ( soon) You can ask (will expire )
Answers in as fast as 15 minutes