CS145 Assignment #3

Due Wednesday, October 22, 1997

Step 3 of Your PDA (Personal Database Application)

Note2: Oracle is not being backed up. You need to save anything you need long-term in the leland file system.

(a)

(15 pts.) Write an SQL database schema for your PDA, using the CREATE TABLE commands described in the handout Getting Started With Oracle. Pick suitable datatypes for each attribute. Page 286 of the text gives you the principal options regarding types. Hand in a printout of the commands you use to create your database schema (it is a good idea to keep this file for the balance of the course). Show the response of sqlplus to a request to describe each of your relation schemas. For example, to see the schema for relation Foo type

     DESCRIBE Foo;

(b)

(10 pts.) Execute about five INSERT commands to insert tuples into one of your relations. Show the response of sqlplus and the relation that results when you issue a SELECT * command. Again, the information on how to do this step is in Getting Started With Oracle.

(c)

(25 pts. Develop a substantial amount of data for your database and load it into your relations using the SQL load command. See The Oracle Bulk Loader for information on how to bulk-load data. To create the data, write a program in any programming language you like that creates large files of records in a format acceptable to the Oracle bulk loader, then load the data into your PDA relations. If you are using real data for your PDA, your program will need to transform the data into files of records conforming to your PDA schema. The rest of you will write a program to fabricate data: your program will generate either random or nonrandom (e.g., sequential) records conforming to your schema. Note that it is both fine and expected for your data values--strings especially--to be meaningless gibberish. The point of generating large amounts of data is so that you can experiment with a database of realistic size, rather than the small ``toy'' databases often used in classes. The data you generate and load should be on the order of:

• At least two relations with thousands of tuples
• At least one relation with hundreds of tuples

If the semantics of your application includes relations that are expected to be relatively small (e.g., schools within a university), it is fine to use some small relations, but please ensure that you have relations of the sizes prescribed above as well. When writing a program to fabricate data, there are two important points to keep in mind:

(1)

Although you have not (yet) declared keys in your relations, in many cases you probably know that an attribute or set of attributes in a relation will serve as a key. If so, be sure not to generate duplicate values for these attributes.

(2)

Your PDA almost certainly includes relations that are expected to join with each other. For example, you may have a Student relation with attribute courseNo that's expected to join with attribute number in relation Course. In generating data, be sure to generate values that actually do join--otherwise all of your interesting queries will have empty results! One way to guarantee joinability is to generate the values in one relation, then use the generated values in one relation to select joining values for the other relation. For example, you could generate course numbers first (either sequentially or randomly), then use these numbers to fill in the courseNo values in the student relation.

Turn in your program code for generating or transforming data, a small sample of the records generated for each relation (5 or so records per relation), and a script showing the loading of your data into Oracle.

Problem Set

1. (15 pts.) Considering the following E/R design and ODL design for a database managing hosts. Note: the RAHosts entity set, representing hosts that the university provides to research assistants (RA's) to do projects at home, is not shown in the E/R, because the properties of any RAHost entity can be decomposed to other entity sets.

   The E/R model is --

   

   The ODL model is --

     interface Domains 
   	   (key name)
       {
           attribute string name;
           relationship Set Hooks
                   inverse Hosts::HookedIn;
       }
       
       interface Hosts 
       {
           attribute string name;
           attribute string OS;
           relationship Domains HookedIn
                   inverse Domains::Hooks;
       }
   
       interface UnivHosts: Hosts 
       {
           attribute int UnivID;
       }
   
       interface ResiHosts: Hosts 
       {
           attribute string Resident;
       }
   
       interface RAHosts: UnivHosts, ResiHosts
       {
       }
   
       

   Please create relational database schemas as follows --
   • E/R style: Convert the E/R model to relational model.
   • ODL style: Convert the ODL model to relational model. Note: class "Host" has no key. Try to make one instead of borrowing one from "Domain" as in E/R.
   • Using nulls: Write one relation (allowing null) representing the class and subclasses, and explain how it represents all the necessary information.

2. (6 pts.) Consider the following E/R schema.

   

   • Explain briefly what the two arrows mean.
   • Convert the relationship TAfor to a relation, and give all the possible keys.

3. (8 pts.) Consider a relation with schema R(A, B, C, D) and functional dependencies A->B, BC->D, D->A.
   • What are all the nontrivial functional dependencies that follow from the given dependencies? You need only consider single attributes on the right side.
   • What are all the keys of R?
   • What are all the superkeys that are not (minimal) keys?

4. (9 pts.) Are the following statements true? If so, prove it. Otherwise, disprove it. Note: You just need a counterexample to disprove a statement.
   • If AB->AC, then B->C.
   • If AB->C, then A->B or A->C.
   • If A->B and BC->D, then ABC->D.

5. (6 pts.) Exercise 3.7.1(e) [p. 154], parts (i) and (ii) only.

6. (6 pts.) Exercise 3.7.4 [p. 155].