Alternate Exam for CSE 480 (2017) KEY

Transcription

1 Alternate Exam for CSE 480 (2017) KEY Answer the questions in the spaces provided on the page. If you run out of room for an answer, continue on the back of that page. Instructions: DO NOT START THE EXAM UNTIL TOLD TO DO SO You need to answer 6 of the 7 questions. On one of the questions make a large slash through it, which indicates that it should not be graded. On every page (including the first and last page), write your first and last name, before answering the question. Unnamed pages may be lost. If you start to answer a question and then change your mind, please cross out the attempt and write DO NOT GRADE across it. Figure 1:

2 Question 1: SQL statement points I ve been collecting data about some of the professors at MSU (in a table named profs ). However, in an I sent to the department, I realized that I shouldn t be referring to them by their first name, because some of the professors share a first name. Please write a query to find the first names that are unique (ordered alphabetically) among the CSE professors. You may not use subqueries or joins in your query. Here is some example data: Table: profs first name last name department Josh Nahum CSE Charles Ofria CSE Bill Punch CSE Rich Enbody CSE Josh EvilTwin CSE Leo Kempel EE Charles Owen CSE Eric Goodman EE Eric Torng CSE Abdol Esfahanian CSE And the desired results for this example data: first name Abdol Bill Eric Rich Fill in the blanks when the clause should be used in the SELECT statement: SELECT FROM WHERE GROUP BY first name profs department = CSE first name HAVING count() = 1 ORDER BY first name ;

3 Question 2: Transaction Modes points After the statement is completed by the associated connection, write which connections are holding each type of lock in the table. If no connection holds a type of lock, leave it blank. A connection can only hold one lock at a time. If an action can t be granted the necessary locks, cross out that action and proceed as if that action wasn t in the schedule (don t perform a rollback). ID SQL statement Shared Reserved Exclusive 1 CREATE TABLE... 1 BEGIN IMMEDIATE TRANSACTION; 1 2 BEGIN TRANSACTION; 1 2 SELECT SELECT COMMIT TRANSACTION; 1 1 DELETE ROLLBACK TRANSACTION; 1 BEGIN EXCLUSIVE TRANSACTION; 1 1 SELECT BEGIN DEFFERED TRANSACTION; 1 1 COMMIT TRANSACTION; 2 UPDATE... 2 BEGIN TRANSACTION 2 SELECT INSERT SELECT COMMIT TRANSACTION; 2 4 SELECT COMMIT TRANSACTION; 3 BEGIN TRANSACTION; 3 SELECT SELECT INSERT BEGIN IMMEDIATE TRANSACTION; COMMIT TRANSACTION; 3 5

4 Question 3: Corrupted Database points Unfortunately, Pikachu got a bit upset too close to our database, and it erased some of the values. The data isn t essential, but we would like to recover what we can. Here s what we know: The relation has 7 attributes (1-7) as shown below. The relation has one multivalued dependency: And, one functional dependency: Use the data given in the relation below to fill in the missing values. If the value is unknown, put a question mark (?) instead of a number J J K D Y F F F A B C O Q W F A C D X X Y F A C D O Q W F A B C X X Y X A B C G Q? A W? D Y A F J X B? Y U F

5 Question 4: Closures points The relation (R) has two functional dependencies, collectively called F. R(A, B, C, D, E, G) A C B E D B G (a) (1 point) Fill in the bubbles of the sets in the attribute set closure {ACDE} +? {ADE} {BG} {B} {ABDE} {CDE} {ABCDEG} (b) (1 point) Fill in the bubbles of the functional dependencies in the closure of F (F + )? D B G A B E D A B B D B D B G C B B (c) (2 points) Which of the following are superkeys? {ACDE} {ABCDEG} {ACD} {BEG} {ACEG} {ABCE} (d) (1 point) Which of the following are keys? {ACDE} {ABCDEG} {ACD} {BEG} {ACEG} {ABCE}

6 Question 5: Multiple Types of Locks points Below are three transactions (and six total actions). Unlocks must happen after all the actions in a transaction have taken place (strict two-phase locking). For this problem, there are shared locks (sl 1 (A)) and exclusive locks (xl 1 (A)) and either/both are unlocked with (u 1 (A)). Below, the order of each of the actions are interleaved. For each part, output the necessary locks and unlocks that the transaction should perform to make the action take place (don t forget to include the action itself). (a) T 2 : r 2 (X) Answer for part a: sl 2 (X); r 2 (X); (b) T 1 : r 1 (X) Solution: sl 1 (X); r 1 (X); u 1 (X); (c) T 2 : r 2 (Z) Solution: sl 2 (Z); r 2 (Z); (d) T 3 : w 3 (Y ) Solution: xl 3 (Y ); w 3 (Y ); (e) T 2 : w 2 (Z) T 1 T 2 T 3 r 1 (X) r 2 (X) w 3 (Y ) r 2 (Z) r 3 (Y ) w 2 (Z) Solution: xl 2 (Z); w 2 (Z); u 2 (X); u 2 (Z); (f) T 3 : r 3 (Y ) Solution: r 3 (Y ); u 3 (Y );

7 Question 6: Qualities points Here s a relation (R), its attributes and its functional dependencies (F): R(A, B, C, D, E, G, H) A B D E A C G G A H For the decompositions below, fill in the bubbles for their respective qualities: (a) (1 point) R 0 (ABDE), R 1 (ABCGH) BCNF Dependency Preserving Fourth Normal Form (b) (1 point) R 0 (ABDE), R 1 (AGH), R 2 (CG), R 3 (ABC) BCNF Dependency Preserving Fourth Normal Form (c) (1 point) R 0 (ABD), R 1 (ABE), R 2 (AG), R 3 (GH), R 4 (BCG) BCNF Dependency Preserving Fourth Normal Form (d) (1 point) R 0 (ABCDE), R 1 (ABGH) BCNF Dependency Preserving Fourth Normal Form (e) (1 point) R 0 (ABDE), R 1 (GAH), R 2 (GCB) BCNF Dependency Preserving Fourth Normal Form

8 Question 7: Converting E/R Diagram points (a) (2 points) Write a relational database schema representing the E/R diagram. Be sure to combine relations when possible. Use the NULLS method to create relations for the subclasses. Solution: Commercial(time slot, station) Features(time slot, station, UPC) Product(UPC, color, size, waist, in seam, discount) (b) (1 point) Can you have a Product which is both a Shirt and a Pants? Yes No (c) (1 point) Must every Product be featured in a Commercial? Yes No (d) (1 point) How many tables would need to be modified to add a shirt, which is also on sale (still using the NULLS method)?

9 If you have finished early, feel free to bring your exam to an instructor. Or you can draw a picture of your favorite Pokémon. Or you can write a limerick about your love of Boyce-Codd Normal Form. Question Points Score SQL statement 5 Transaction Modes 5 Corrupted Database 5 Closures 5 Multiple Types of Locks 5 Qualities 5 Converting E/R Diagram 5 Total: 30