1. DB Review Session

2. ER Diagrams 1 Where does the salary attribute belong? Actor id name address birthday Acted In Movie title type year salary

3. id name Actor Acted In Movie The entities in a relationship set identify the relationship How would we store information about a person who acted in one movie in several roles? role title Role title ER Diagrams 2

4. id name Actor Acted In Movie The entities in a relationship set identify the relationship role title ER Diagrams 2

5. id name Actor Acted In Movie The entities in a relationship set identify the relationship How would we store information about a person who acted in one movie in several roles? title Role title ER Diagrams 2

6. ER Diagrams 3 Person id name age FatherOf Where would you put the arrow? father child

7. ER Diagrams 3 Person id name age FatherOf father child

8. ER Diagrams 4 Director id name produced Movie title Actor idname What does this mean? A movie has at most one actor and one director

9. What does this diagram mean? Director id name Directed Movie title A movie has exactly one director. A director directs at least one movie. ER Diagrams 5

10. Copy copy numbercondition Copy Of Borrowed Person id Book title author isbn Owned By Library name ER Diagrams 6

11. snopno S1 S2 S3 S4 P1 P2 P3 P4 P1 P2 P4 P2 pno sno  = Division 1

12. snopno S1 S2 S3 S4 P1 P2 P3 P4 P1 P2 P4 P2 pno sno  = Division 1 S1 S2 S3 S4

13. snopno S1 S2 S3 S4 P1 P2 P3 P4 P1 P2 P4 P2 P4 pno sno  = Division 2

14. snopno S1 S2 S3 S4 P1 P2 P3 P4 P1 P2 P4 P2 P4 pno sno  = Division 2 S1 S4

15. snopno S1 S2 S3 S4 P1 P2 P3 P4 P1 P2 P4 P1 P2 P4 pno sno  = Division 3

16. snopno S1 S2 S3 S4 P1 P2 P3 P4 P1 P2 P4 pno sno  = Division 3 S1 P1 P2 P4

17. SQL Aggregation 1 SELECT B.bid, COUNT(*) FROM Boats B, Reserves R WHERE R.bid=B.bid and B.color=‘red’ GROUP BY B.bid What does this query return? Tuples: (id of a reserved red boat, # of reservations of the red boat)

18. SELECT B.bid, COUNT(*) FROM Boats B, Reserves R WHERE R.bid=B.bid GROUP BY B.bid, B.color HAVING B.color=‘red’ SQL Aggregation 2 What if we put the condition into the HAVING clause? We have also to put the color in the grouping list!

19. Aggregation 3 SELECT color FROM Boats B GROUP BY color HAVING max(count(bid)) What is wrong with this? How would you fix it? The Color for which there are the most boats

20. SELECT color FROM Boats B GROUP BY color HAVING count(bid) >= ALL (SELECT count(bid) FROM Boats GROUP BY Color) SQL Aggregation 3 The Color for which there are the most boats

21. Compute Closure(X, F) C := X while there is a V  W in F such that (V  C)and (W  C) do C := C  W return C Attribute Closure 1

22. R=ABCDE F={AB  C, CE  B, D  A, BC  E} Attribute Closure 2  {A} + =  {A,B} + =  {B,D} + = {A} {A,B,C,E} {A,B,C,D,E}

23. IsDependencyPreserving(F,R 1…k ) for each X->Y in F do if not IsPreserved(X,Y,R 1…k ) return false return true Dependency Preservation 1a

24. /* check if X->Y is preserved */ IsPreserved(X,Y,R 1…k ) Z:=X while changes to Z occur do for i=1 to k do Z:= Z  ((Z  R i ) +  R i ) if Y  Z return true else return false Dependency Preservation 1b

25. Is the following decomposition dependency preserving? R = ABCDE F = {A -> ABCDE, BC -> A, DE -> C} R 1 = ABDE, R 2 = DEC Dependency Preservation 2 No! BC->A is not preserved

26. R = ABC. For each F below, decide whether R is in BCNF/3NF: Normal Forms  F = {}  F = {A -> B}  F = {A -> B, A -> C}  F = {A -> B, B -> C}  F = {A -> B, BC -> A}