CS145 Assignment #3

Due Wednesday, October 21, 1998

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)

(10 pts.) Reconsider your relation schema in the light of the theory of normalization and BCNF. Remind us of your chosen database schema. For each of your current relations, tell whether its relation schema is in BCNF. If not, then either redesign your schema so the relation is in BCNF, or give a rationale for leaving in in non-BCNF form (e.g., the amount of redundancy introduced is minimal, and splitting the relation would cause some reasonable queries to become multirelational). Indicate your final choice of design, whether or not you choose to decompose one or more relations.

(b)

(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;

(c)

(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.

(d)

(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

Employee(SSN, name, salary, DNo) 
Department(DNo, DeptName, MgrSSN) 
Project(PNo, location, ProjName) 
HourLog(SSN, PNo, hours) 

The Employee relation provides a list of employees with their SSN, name, salary, and department number (DNo). The SSN is unique for each employee. Each employee belongs to only one department. The Department relation contains a list of the departments for the company. Its schema includes a unique department number called DNo. It also includes the name of the department (DeptName) and the social security number of the department's manager (MgrSSN). Each department has a only one manager. The Project relation includes a unique project number (PNo), location and the project name (ProjName). An employee can be assigned to any number (including zero) projects. Each project has at least one person assigned to it. Finally, the HourLog relation lists for each project the number of hours of work for each employee who is assigned to that project. The key of this relation is SSN and PNo.

All 10 queries are 4 points each.

PART A: Write the following queries in Relational Algebra. You may use assignment of intermediate results for long queries.

1. Find the name and the SSN of everyone who works more than 100 hours on one particular project.
2. Find the name and SSN of everyone who works for department number 1 and also work on project number 2.
3. Find the name and the SSN of everyone who works on at least two projects.
4. Find the SSN of everyone who is not working on any project.
5. Find the name and the SSN of everyone who works on every project.
6. Find employees and their managers who work the fewest hours for each project. A tuple of (EmployeeSSN, EmployeeName, ManagerName, PNo) should be listed for every project.

PART B: Write queries 1-4 from above in SQL: