1 / 16

Relational Algebra Relational Calculus

Chapter Five. Relational Algebra Relational Calculus. Objectives Fundamental operations in RA Union Set difference Select Project Cartesian Product Relational Calculus. Query Languages. Procedural Relational Algebra (RA) Non-Procedural Tuple Relational Calculus

odessa-valenzuela
Télécharger la présentation

Relational Algebra Relational Calculus

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter Five Relational AlgebraRelational Calculus Objectives Fundamental operations in RA Union Set difference Select Project Cartesian Product Relational Calculus

  2. Query Languages • Procedural • Relational Algebra (RA) • Non-Procedural • Tuple Relational Calculus • Domain Relational Calculus

  3. Fundamental Operations in RA • Binary Operations • UNION • MINUS • CARTESIAN PRODUCT • Unary Operations • SELECT • PROJECT

  4. Union of R S • Union of R  S • All tuples in R or S • Union Compatible • Some degree • Attributes of R&S must be the same

  5. Union of R  S

  6. Union of R  S name (faculty) name (staff)

  7. Set Difference (MINUS) R - S • Set of tuples in R but not in S • Union Compatible

  8. Faculty  Staff Name ID Salary Smith 1 70,000 R  S = R – (R – S) Intersection: R  S • Set of of tuples belong to both R & S • Union Compatible Find the list of faculty members who are also staff

  9. Cartesian Product R x S • Set of (K1 + K2) tuples: The first K1 tuples are from R. The last K2 tuples are from S

  10. Cartesian Product R x S List of courses offered in year 99?

  11. Selection (Unary Relation) • Select tuples that satisfy a given predicate major = ‘COSC’ (Student) • Result is another relation • Conditions are relational operator (,, ,  , ) • Logical operators AND (), OR(), NOT()

  12. Selection (Unary Relation) • Find all Faculty members which make less than $45,000 salary < 45,000(Faculty) • Find all staff who make less than $40,000 and ID > 100 salary < 40,000 AND ID > 100 (Staff) • List of number of courses offered in year 99 S_Num = S_Num AND year = 99 (Semester x Semester_Course)

  13. Projection (Unary) • Select attributes • (Pi) • Find the number of faculty that teach COSC courses • name( course=‘COSC’(Faculty))

  14. Theta Join • R S • Theta join allows us to combine the selection & the cartesian product into an operation If  is = It is called Equijoin If the attributes have the same name, the join is called Natural Join

  15. Part Two Relational Calculus (RC) • Non-procedural • Most commercial query language • Types: • Tuple RC: Variables represent tuples • Domain RC: Variables represent values of domain

  16. Tuple Relational Calculus: { t | P(t)} Examples • List of students with GPA > 3 { t | t Є student ^ t[GPA] > 3 } • List of students name with GPA > 3 { t | s Є student (t[NAME] = s[NAME] ^ t[GPA] > 3)}

More Related