CITS2232 Databases Mid-semester 2010

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1 CITS2232 Databases Mid-semester 2010 This paper consists of 6 pages and 3 questions. You should complete every question (total of 30 marks). Answer each question in the space provided. Family Name: First Name(s): Student Number: Question 1 (8 marks) Draw a single ER diagram that best captures the following situation of students, advisors and units covering a university calendar year. Students each have a unique student id (sid), advisors have a unique employee id (eid), and each course work unit has a unique id (uid). At any time in the year each student must be assigned one advisor who counsels students about degree requirements and academic matters. Each term, each student must register for course work units with the help of their academic advisor, but if the student s assigned advisor is not available, the student may register with any advisor. Each unit is delivered in one term of the year, with no repeats. We must keep track of students, the assigned advisor for each, the name of the advisor who registered them for the unit and the term for which they registered in that unit. Notes: Draw your ER Diagram in the style adopted in the lecture notes (not your own favourite style). Draw it as one connected picture, not as a collection of isolated pieces. Clearly indicate the Entity and the Relationship keys and attributes, if any. Recall you are being asked for an ER Diagram, and not for a database schema. PUT YOUR ANSWER ON THE NEXT PAGE 1

2 ANSWER QUESTION ONE HERE 2

3 Question 2 (10 marks) Consider the following DB schema for patients and their physicians. Each patient can be assigned more than one physician. The same-named fields in relations are keys to each other. Physician(fid) is a key to Person(id). Person (id: integer, name: string, birth: date, address: string) Patient (id: integer, fid: integer, assign: date) Physician (fid: integer, specialty: string, contact: integer) 1. Write the MySQL statements necessary to create the Patient table. Ensure referential integrity is maintained and that the Patient entry is deleted if the person leaves. The assigned physician is set to NULL, if the physician resigns (this will likely cause the server to fire a trigger). CREATE TABLE Patient ( id INT, fid INT, assign DATE, PRIMARY KEY (id, fid), FOREIGN KEY (id) REFERENCES Person (id) ON DELETE CASCADE, FOREIGN KEY (fid) REFERENCES Physician (fid) ON DELETE SET NULL ) Engine = InnoDB; 3

4 2. What will result from following insertion command? What do you think should result from this insertion command? INSERT INTO Patient VALUES (789123, , ) It will successfully insert the values , and into a new row. The insertion should result in a warning or error message identifying that a patient has been assigned to themselves as the attending physician. 3. Write the relational algebra expression that yields all the dates that patients were assigned to a doctor named Schweizer. π assign (σ fname= Schweizer (P atient P hysician fid=id P erson)) OR π assign ((σ fname= Schweizer P erson) id=fid P atient) 4. State what the following query will compute? (ENT is the acronym for Ear, Nose and Throat.) π sname (P erson (π id,fid P atient/π fid (σ specialty= ENT P hysician))) Find the names of all the patients who have seen (been assigned to) EV- ERY ear, nose and throat specialist. 4

5 Question 3 (12 marks) Consider the following relation containing data concerning the leaders of some fictitious nation. Leaders may share a last name (lname) and/or a first name (fname) but no leader shares a birth date. The inauguration date is the date they became leader. Assume an individual can be leader for only one term. Leaders(lname: string, fname: string, birth: date, death: date, inauguration: date, state: string) Write MySQL queries to do each of following things: 1. Find the last name and the first names of leaders who share a common last name. SELECT LA.lname, LA.fname, LB.fname FROM Leaders LA, Leaders LB WHERE LA.lname = LB.lname AND LA.birth < LB.birth; The < eliminates the duplicates. Using <> will duplicate every entry. 2. List the states and the number of leaders from each state. Only states that have had more than one leader are to be included. The list should be in descending order from the most frequent state. SELECT L.state, COUNT (*) FROM Leaders L GROUP BY L.state HAVING COUNT (*) > 1 ORDER BY COUNT(*) DESC; 5

6 3. Find the last and first names of the leaders who have the longest last names. SELECT LA.lname, LA.fname FROM Leaders LA WHERE LENGTH(LA.lname) = ( SELECT LENGTH(LB.lname) FROM Leaders LB ORDER BY LENGTH(LB.lname) DESC LIMIT 1); OR SELECT LA.lname, LA.fname FROM Leaders LA WHERE LENGTH(LA.lname) = ( SELECT MAX(LENGTH(LB.lname)) FROM Leaders LB); 4. List the leaders whose inauguration can be attended by (living) past leaders. SELECT LA.lname, LA.fname FROM Leaders LA WHERE EXISTS ( SELECT LB.lname FROM Leaders LB WHERE LB.inauguration < LA.inauguration AND (LB.death > LA.inauguration OR LB.death IS NULL) ); The OR LB.death IS NULL is needed for the later leaders where previous deaths haven t happened yet. END OF TEST PAPER 6

CITS3240 Databases Mid-semester 2008

CITS3240 Databases Mid-semester 2008 This paper consists of 6 pages and 3 questions. You should complete every question (total of 40 marks). Answer each question in the space provided. Name: Student Number: