08.71.31 Introduction to databases

Homework 1


In the first week we cover Chapter 1 in the textbook Database Management Systems. The following exercises are from that material.
  1. Exercise 1.4 on page 23 in the textbook.
    [Explain the difference between external, internal, and conceptual schemas. How are these different schema layers related to the concepts of logical and physical data independence? ]
  2. Exercise 1.6 on page 23 in the textbook.
    [Scrooge McNugget wants to store information (names, addresses, descriptions of embarrassing moments, etc.) about the many ducks on this payroll. Not surprisingly, the volume of data compels him to buy a database system. To save money, he wants to buy one with the fewest possible features, and he plans to run it as a stand÷alone application on his PC clone. Of course, Scrooge does not plan to share his list with anyone. Indicate which of the following DBMS features Scrooge should pay for; in each case, also indicate why Scrooge should (or should not) pay for that feature in the system he buys. 1) A security facility. 2) Concurrency control. 3) Crash recovery. 4) A view mechanism. 5) A query language. ]
  3. Give at least three disadvantages of DBMSs and explain each of them.

  4. Write a short (10-20 lines) overview of the life of Edgar F. Codd.

  5. Give at least three advantages that the relational model has over the older models i.e. the network model and the hierarchical model

Hand your solutions to the section teachers on monday Sept. 3rd.

hh (hja) hi.is, August 27th, 2007.