Download CSc 460 (Database Design) Module 3 (SQL) Review Fall 2012 1

CSc 460 (Database Design)
Module 3 (SQL) Review
Fall 2012
1. Show how the following query (on the WebReg schema) can be expressed in
the relational algebra with a semi-join.
"List the names of buildings in which sections of computer
science courses are held."
What about an SQL query suggests that it may be mapped to a semijoin?
Illustrate with an SQL query for the above expression.
2. Short answer.
What construct does each of the keywords in SQL queries correspond to in
the tuple relational calculus? For example, "SELECT” corresponds to "{".
Give four keywords (other than "SELECT").
3. Consider the videostore schema on slide R-70 and 71 and the following
query.
project_Title (
( (ChildOf EquiJoin_{Parent = Customer.CustomerID}
select_{Name="BillSmith"}(Customer)
) EquiJoin_{Child=Rents.CustomerID} Rents
)
NaturalJoin Film
)
[4]
[4]
query
a. Express this query in SQL.
b. Express this query in natural English. (Can you express this
in only eight words?)
Assume the following cardinalities.
ChildOf
Customer
Rents
Film
[6]
287
1223
467
8250
c. Provide a lower and an upper bound on the cardinality of the
result of your query. Justify your answer.
4. Views are provided in SQL to achieve logical data independence.
[6] a. What is the practical utility of logical data independence?
Give a concrete example.
CSc 460 (Database Design)
Module 3 (SQL) Review
Fall 2012
[3] b. Express the view, called ForeignFilm, on the video store
schema,
in SQL, containing the FilmID, RentalPrice, and Title of all
foreign films.
[3] c. Express this query, using this view, in SQL: "List the names of
all customers who have reserved a foreign film".
[5] d. Use query modification to translate the query in (c) into a
query
on the base tables.
5. Map the following SQL query into (normal!) English, relational
algebra, and domain relational calculus.
SELECT Kind
FROM Reserved, Film
WHERE Film.FilmID = Reserved.FilmID
AND CustomerID = ANY (SELECT CustomerID
FROM Customer
WHERE ZipCode = 85718)
6. SQL differentiates the notions of database schemas and table schemas.
[4] a. Provide one similarity and one difference between these two
notions.
CSc 460 (Database Design)
Module 3 (SQL) Review
Fall 2012
[2] b. Provide an SQL statement to define a database schema called
Class associated with the user name Rick.
[4] c. Differentiate briefly what takes place with the Class schema
when it is dropped cascaded versus dropped restricted.
7. The DBMS stores the relational schema as a set of tables.
Tables (TableName, Owner)
Columns (TableName, ColumnName, DataType, Width)
[8] a. Express the following query in relational algebra, tuple
relational calculus, domain relational calculus, and SQL.
List the columns of data type "INTEGER" in tables owned by Rick.
[2] b. Explain precisely why the domain calculus expression is the
shortest.
[7] c. Express the following query in SQL: List the tables that
contain a column for every data type listed in the Columns
table.
[5] Extra credit. Express this query in the relational algebra.
CSc 460 (Database Design)
Module 3 (SQL) Review
Fall 2012
[6] d. Give an SQL query on this schema that is not possible to
express in either relational algebra, domain relational
calculus or tuple relational calculus. Explain your reasoning.
Also give the English version of your query. Your query should
make sense.
8. Expressive power is an important consideration in query language
design.
[2]
a. SQL is relationally complete. Explain what that means.
[10] b. Prove that SQL is relationally complete.
[5]
c. Show that nested selects in the FROM clause do not add any
expressive power, by converting the following SQL query into
one not using a nested select.
SELECT Name
FROM Customer, (SELECT *
FROM Reserved
WHERE ResDate = DATE '1998-10-14') AS R
WHERE Customer.CustomerID = R.CustomerID
AND Customer.City = 'Tucson'
[1]
d. Express the above SQL query in colloquial English (not
geek-speak).
[8] e. Also express this query in relational algebra, relational
tuple calculus, and relational domain calculus.
CSc 460 (Database Design)
[4]
Module 3 (SQL) Review
Fall 2012
f. Does the MAX aggregate add any expressive power to SQL? Why
or
why not?
9. Express the following query in tuple relational calculus, tuple domain
calculus, relational algebra, and SQL. The query concerns the
relations Student(SName, SID), Class(CName, Instructor, Room), and
Grade(SID, CName, Grade).
List all students who made an A in a class taught by Rick.
List the students who made an A in all classes taught by Rick.
Which version is the SQL query the most similar to? Which version
is the most concise?