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CSC 3810 Lecture Slides Relational Algebra

CSC 3810 Lecture Slides Relational Algebra. Instance S1 of Stations.  network = “NBC” (S1) . What stations are in the NBC network?.  network, town (S1) . What networks in what towns are represented?.  network (S1) . What networks are represented?.

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CSC 3810 Lecture Slides Relational Algebra

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  1. CSC 3810 Lecture SlidesRelational Algebra

  2. Instance S1 of Stations

  3. network = “NBC” (S1) What stations are in the NBC network?

  4. network, town (S1) What networks in what towns are represented?

  5. network (S1) What networks are represented?

  6. channel, town(network = “ABC” (S1)) What channels are ABC in what towns?

  7. Instances S1 and S2 of Stations

  8. S1  S2

  9. S1  S2

  10. S1 – S2

  11. Instance P1 of Programs Programs ( statid:integer, showid:integer, timeslot:integer,day:string )

  12. S2  P1

  13. Instance T1 of TVShows TVShows ( showid:integer, title:string )

  14. P1⋈P1.showid=T1.showid  T1.title=”West Wing” T1 When is the West Wing on?

  15. S1 ⋈ S1.statid = P1.statid P1 When is each station showing something?

  16. (S1 ⋈ P1) ⋈ T1 What shows are being shown on which stations, when?

  17. Instance D1 of DVDs DVDs (did: integer, title: string)

  18. Instance P1 of People People (pid: integer, name: string)

  19. Instance O1 of Owns Owns (pid: integer, did: integer)

  20. O1 ⋈ D1 Who owns which DVD? (first try)

  21. O1 ⋈ D1 ⋈ P1 Who owns which DVD? (with names this time)

  22. name,title (O1 ⋈ D1 ⋈ P1) Who owns which DVD?

  23. title=“The Matrix”(name,title(O1 ⋈ D1 ⋈ P1)) Who owns “The Matrix?”

  24. name=“Bob”(name,title(O1 ⋈ D1 ⋈ P1)) Which movies does Bob own?

  25. name=“Ellen” (O2) name=“Mary” (O2) Ellen and Mary have combined their movie collection. What is in their joint collection?

  26. name=“Ellen” (O2) name=“Mary” (O2) Which movies do they have duplicates of?

  27. pid (title=“The Matrix” (D1) ⋈ O1) Who owns “The Matrix?” Name this “MatrixOwners”

  28. pid (title=“Star Wars” (D1) ⋈ O1) Who owns “Star Wars?” Name this “StarWarsOwners”

  29. name (MatrixOwners  StarWarsOwners ) ⋈ P1) Who owns both “The Matrix” and “Star Wars?”

  30. ρ(Ownership, pid,.name,did (O1⋈P1)) Who owns which movies? Name this “Ownership”

  31. ρ( Pairs (1→pid1, 2→name1, 3→did1, 4 → pid2, 5→name2, 6→did2), Ownership  Ownership ) What are all pairs of owned movies?

  32. name1 (pid1=pid2  did1did2( Pairs ) ) Who owns at least two movies?

  33. Division Who are the people in O1 (left) where for every did in D1 (below), there is a tuple in O1? I.e., who owns every movie?

  34. Division pid (O1)  did (D1) (  pid (O1)  did (D1) ) – O1  pid ((  pid (O1)  did (D1) ) – O1 ) O1 / (  did (D1) )  name ( O1 / (  did (D1) ) ) ⋈ P1 )

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