Final exam CSCC43 S14

Transcription

1 Final exam CSCC43 S14 You have 2h 50m (170 minutes) to complete this exam. Skip any question you do not know how to answer, or you will run out of time. Assume bag semantics for any problem where the distinction matters. 1. Relational schema inference (10 minutes) Given the following relational expression, populate the table. For each attribute table pair in the table, place a if the attribute is definitely part of the table s schema, a if the attribute is definitely *not* part of the table s schema, and a? if there is insufficient information to decide. A B C D a b c x y z 2. Evaluating RA expressions (5 minutes) Evaluate the following RA expression, given the input data shown. Give both the schema and rows of T. X(a,b,d) Y(d,x) Z(a,b,c,d) T( ) 3. Creating RA queries (24 minutes, 6 minutes each) Consider the following relations: FamousPerson(pid, name, ) Reporter(rid, name, ) CaughtOnCamera(pid, rid, timestamp, ) Give RA queries that answer the following questions. For brevity you may use F/R/C as table names. Timestamps and date strings can be converted to Julian days with the function julianday() (as part of exam prep, you may want to execute select julianday( ) and see what sqlite3 returns).

2 4. Converting RA to SQL (12 minutes, 6 minutes each) Convert each of the following two RA expressions into equivalent SQL. You may find it helpful to create common table expressions using the with clause (like temporary views, check out the sqlite3 docs!) 5. Debugging SQL queries (18 minutes, 6 minutes each) Each of the following queries is semantically correct (no typos or syntax errors) but contains a severe logical bug that causes it to produce a very wrong result. Find and correct the bug in each query. 6. Creating SQL queries directly (20 minutes, 5/5/10) Let s come back to the relations from Problem 3. As with problem 4, you may find it useful to employ common table expressions. FamousPerson(pid, name, ) Reporter(rid, name, ) CaughtOnCamera(pid, rid, timestamp, ) Write SQL queries that answer the following questions: 7. E/R modeling (15 minutes) Create an E/R model that captures the requested information about the problem domain described below. All entity sets must have a primary key. Make sure to also express reasonable cardinality constraints and to identify attributes for entity and relationship sets as appropriate. 8. Converting E/R to SQL/DDL (15 minutes) Convert the following E/R diagram into an SQL/DDL description of a relational schema, including all constraints expressed in the diagram: 9. Fun with triggers (10 minutes) We discussed in class how an instead of trigger can be used to allow users to update a view. The examples in class updated other tables, though (not the view the trigger covers). This question is about what happens when a trigger inserts into the same table it protects. It is known as a recursive trigger (and yes, you might want to Google that term as part of your exam prep). Just as with any form of recursion, it s easy to cause an infinite loop if you re not careful. Given a problem description, you ll need to identify some sort of recursive case that says when the recursion should continue, and a base case that says when to stop. With that context, suppose we have the following schema:

3 10. Schema normalization (10 minutes) a) Find two different minimal bases for the following FD set: b) Given the schema R(a,b,c) and S(b,d), plus the FDs..., give an example of data that can be inserted into the database but which violates the FDs. Your answer should involve no more than three tuples containing binary field values. 11. XPath/XQuery (16 minutes, 4 minutes each) For each of the following, give an XPath or XQuery expression that answers the question about reed.xml (a sample course entry can be found in the appendix). You may assume that local:distinct is available.

4 12. XQuery madness (15 minutes) Write an XQuery that reads words from an XML file and... The input XML file has the following structure: <words> <verb>studied</verb> <noun>time</noun> <adjective>tired</adjective> <verb>stared</verb> <adverb>blankly</adverb> <noun>student</noun> <noun>final exam</noun>... </words> In case it s been a while since your last English grammar class, here are definitions for the word types: Noun: person, place, thing, or idea (student, car, database, etc.) Verb: an action (eat, jump, run, fight, etc.) Adjective: describes a noun (red, green, big, small, ugly, pretty, etc.) Adverb: describes a verb, usually ends in ly (slowly, greedily, infuriatingly, happily, etc.) Your template should use entries for a given word type (noun, verb, adjective, adverb) in the order they appear in the input XML (e.g. studied must be used before stared in the above example). You may assume that the input file contains enough words of each type so that your XQuery will not run out. NOTES: You may assume local:distinct is pre defined, but you may want to define helper function(s) XQuery expects XML as output; all plain text has to be wrapped in a tag of some kind. The text portion of your output should not include tags like <noun>, <verb>, etc.

5 Appendix: schema information This page contains schema information only. There are no questions on this page. You may tear this page off while working. Store schema Region(regionkey, rname) Nation(nationkey, regionkey, nname) Supplier(suppkey, snationkey, sname) Part (partkey, ptype) PartSupp(partkey, suppkey, stock_qty, unit_cost) Customer(custkey, cnationkey, cname, m_segment) Orders(orderkey, custkey, orderdate, priority) LineItem(orderkey, line_num, partkey, suppkey, qty, ext_price, commit_date, ship_date, receipt_date, return_flag) Hockey schema Olympics(oID, city, country, year) Team(tID, country, oid, coach) Player(pID, name, position) PlaysOn(pID, tid) Game(gID, date, oid, ht, at, hscore, ascore) Goal(gID, period, time, score, assist, goalie) Results(oID, tid, place) Sample entry from reed.xml <course> <reg_num>10577</reg_num> <subj>anth</subj> <crse>211</crse> <sect>f01</sect> <title>introduction to Anthropology</title> <units>1.0</units> <instructor>brightman</instructor> <days>m W</days> <time> <start_time>03:10pm</start_time> <end_time>04:30</end_time> </time> <place> <building>eliot</building> <room>414</room> </place> </course>