Exercises 1 

( Relational Algebra )

Questions

Consider the following collection of relation schemes:

professor(profname, deptname)
department(deptname, building)
committee(profname,commname)

  1. (2 points) Find all the professors who are in any one of the committees that Professor Smith is in.

  2. (3 points) Find all the professors who are in at least all those committees that Professor Smith is in.

  3. (4 points) Find all the professors who are in exactly (i.e., no more and no less) all those committees that Professor Smith is in.

  4. (3 points) Find all the professors who have offices in at least all those buildings that Professor Smith has offices in.

Answers

  1. R2 <- commname(profname = Smith(committee))
    profname(committee R2)

  2. R2 <- commname(profname = Smith(committee))
    committee / R2

  3. R2 <- commname(profname = Smith(committee))
    R3 <- commname(committee) - R2
    (committee / R2) - profname(committee R3)

  4. R4 <- profname, building(professor department)
    R5 <- profname = Smith(professor) department
    R4 / building(R5)