Homework 1 - Relational Algebra

Do problem 2.4.3, all parts [that is, (a) through (i)].
  (This is on page 55 of the textbook, though you may find it
  helpful to refer to the description of the database relations
  on page 37.)

  You may find it helpful to use the "linear notation
  for algebraic expressions" described in section 2.4.13 (starting
  on page 51).  We did not explicitly discuss this in class, but
  this notation simply lets you give temporary names to parts of
  a relational algebra expression, thus letting you build a big
  expression out of smaller pieces, which is usually easier to 
  manage than writing one huge expression.

  Remember, you are writing relational algebra expressions, not
  SQL queries.

  CLARIFICATIONS AND HINTS (JANUARY 28):
  
  * For each problem, you need to write a relational algebra query,
    and show the results of the query using the sample data on pages
    56 and 57.  However, for part (f), you do not need to show the
    results because they are very long.  :)
  
  * Note that the problem specifies there are "dangling tuples" in
    the data.  You are not expected to use outer joins to handle 
    these situations; use natural or theta joins and simply disregard
    situations where the database doesn't have the information you
    need to answer the query.  For instance, in the sample data, there 
    are three ships listed in the Outcomes relation that fought in the
    battle of Guadalcanal, but only two of them have corresponding
    entries in the Ships relation.  For problem (e), your query
    should only return tuples for which you can *find* the displacement
    and number of guns, which means your query will return only
    information on two of the ships, not all three.

  * For parts (g) and (i), note that there are no ships in the sample 
    data that fit the query, so you do not have to show the results
    for these problems either.


Do problem 2.4.5.