Database solution by m.moses wills

1 Edition
MWEBAZE WILLS MOSES
MBARARA UNIVERSITY OF SCIENCE AND
TECHNOLOGY
DATABASE SOLUTION
BY MWEBAZE WILLS MOSES

DATABASE SOLUTION BY MWEBAZE MOSES WILLS

Solutions to Workshop Exercises
Chapter 1: SQL and Data........................................................... 3
Chapter 2: SQL: The Basics ....................................................... 5
Chapter 3: The WHERE and ORDER BY Clauses ............................ 7
Chapter 4: Character, Number, and Miscellaneous Functions.......... 9
Chapter 5: Date and Conversion Functions .................................12
Chapter 6: Aggregate Functions, GROUP BY and HAVING .............15
Chapter 7: Equijoins ................................................................18
Chapter 8: Subqueries .............................................................24
Chapter 9: Set Operators .........................................................28
Chapter 10: Complex Joins .......................................................31
Chapter 11: Insert, Update, and Delete......................................35
Chapter 12: Create, Alter, and Drop Tables.................................38
Chapter 13: Indexes, Sequences, and Views ...............................40
Chapter 14: The Data Dictionary, Scripting, and Reporting ...........42
Chapter 15: Security................................................................45
Chapter 16: Regular Expressions and Hierarchical Queries............47
Chapter 17: Exploring Data Warehousing Features ......................50
Chapter 18: SQL Optimization...................................................52

Chapter 1: SQL and Data
In this chapter, you learned about data, how data is organized in
tables, and how the relationships among the tables are depicted in a
schema diagram. Based on your newly acquired knowledge, design a
schema diagram based on the fictional ACME Construction Company.
Draw on your own work experience to design the following
components.
1. Draw boxes for these three tables: EMPLOYEE, POSITION, and
DEPARTMENT.
Solution: See the solution for Exercise 3.
2. Create at least three columns for each of the tables and designate a
primary key for each table.
Solution: See the solution for Exercise 3.
3. Create relationships among the tables that make sense to you. At
least one table should have a self-referencing relationship. Hint: Be
sure to include the necessary foreign key columns.
Solution:
4. Think about which columns should not allow NULL values.

Solution: By definition all the primary key columns do not allow null
values. In the DEPARTMENT table the DEPARTMENT_NAME column
should probably not allow null values.
In the EMPLOYEE table the FIRST_NAME and LAST_NAME columns are
two more candidates for NOT NULL columns because all employees
should have names.
The foreign key columns DEPARTMENT_ID and POSITION_ID must be
NOT NULL as the relationships in the above diagram indicates. The
diagram states that for an individual row in the EMPLOYEE table
always a row must exist in the POSITION table and the DEPARTMENT
table.
The MANAGER_ID column on the other hand must allow nulls as
indicated with the optional recursive relationship. If this was not an
optional relationship, you would not be able to enter the president of
company for instance, because it requires an existing entry for the
President's manager. Therefore, the top of the org chart hierarchy
(e.g., the president) has a null value in the MANAGER_ID column.
It would be wise to not allow null values for the DESCRIPTION column
of the POSITION table as a description should always be entered when
a position is created.

Chapter 2: SQL: The Basics
1. Use SQL Developer to retrieve all the STATE values from the
ZIPCODE table, without repeating the values.
Solution:
The query retrieves 10 distinct state values.
2. Recall one of the statements you used in Lab 2.1, using the SQL
History tab.
Solution:
The SQL commands are saved even after you exit SQL Developer and
you use the SQL History tab to retrieve the statement. If the tab is
not visible, you can click on View, then SQL History or press F8.
3. What happens if you try to logon to SQL*Plus with the uppercase
version of the password learn?
Solution:
You will see an error message indicating that the password is invalid.
By default, the Oracle database 11g has case-sensitive passwords.

4. Execute the following statements in SQL*Plus and record your
observations.
SET NULL 'NULL'
SELECT DISTINCT cost
FROM course
Solution:
The SET NULL SQL*Plus command substitutes the display of any null
values with another value, such as the literal ‘null’ in this example. The
column’s null value is not changed in the database; this command only
changes the SQL*Plus display value.
PD:

Chapter 3: The WHERE and ORDER BY
Clauses
1. Create a SQL statement that retrieves data from the COURSE table
for courses that cost 1195 and whose descriptions start with Intro,
sorted by their prerequisites.
Solution:
SELECT *
FROM course
WHERE cost = 1195
AND description like 'Intro%'
ORDER BY prerequisite;
2. Create another SQL Statement that retrieves data from the
STUDENT table for students whose last names begin with A,B, or C,
and who work for Competrol Real Estate, sorted by their last names.
Solution:
SELECT *
FROM student
WHERE (last_name like 'A%'
OR last_name like 'B%'
OR last_name like 'C%')
AND employer = 'Competrol Real Estate';
3. Write a SQL statement that retrieves all the descriptions from the
GRADE_TYPE table, for rows that were modified by the user
MCAFFREY.
Solution:
SELECT description
FROM grade_type
WHERE modified_by = 'MCAFFREY';
4. Save all three SQL statements in a file called Workshop_Ch3.sql
Solution:

Chapter 4: Character, Number, and
Miscellaneous Functions
1. Write the SELECT statement that returns the following output
ONE_LINE
---------------------------------------------
Instructor: R. Chow...... Phone: 212-555-1212
Instructor: M. Frantzen.. Phone: 212-555-1212
Instructor: F. Hanks..... Phone: 212-555-1212
Instructor: C. Lowry..... Phone: 212-555-1212
Instructor: A. Morris.... Phone: 212-555-1212
Instructor: G. Pertez.... Phone: 212-555-1212
Instructor: N. Schorin... Phone: 212-555-1212
Instructor: T. Smythe.... Phone: 212-555-1212
Instructor: I. Willig.... Phone: 212-555-1212
Instructor: T. Wojick.... Phone: 212-555-1212
Solution:
SELECT RPAD('Instructor: '
||SUBSTR(first_name,1,1)
||'. '
||last_name, 25,'.')
|| 'Phone: '
|| SUBSTR(phone,1,3)
||'-'
||SUBSTR(phone, 4,3)
||'-'
||SUBSTR(phone, 7) ONE_LINE
FROM instructor
ORDER BY last_name
2. Rewrite the following query to replace all occurrences of the string
Unix with Linux.
SELECT 'I develop software on the Unix platform'
FROM dual
Solution:
SELECT REPLACE('I develop software on the Unix platform',
'Unix', 'Linux')
FROM dual
REPLACE('IDEVELOPSOFTWAREONTHEUNIXPLATFO

----------------------------------------
I develop software on the Linux platform
1 row selected.
3. Determine which student does not have the first letter of her or his
last name capitalized. Show the STUDENT_ID and LAST_NAME
columns.
Solution:
SELECT student_id, last_name
FROM student
WHERE SUBSTR(last_name,1,1) = SUBSTR(LOWER(last_name),1,1)
STUDENT_ID LAST_NAME
---------- -------------
206 annunziato
1 row selected.
In Chapter 16, “Regular Expressions and Hierarchical Queries,” you will
learn about regular expressions which can accomplish the same result.
4. Check whether any of the phone numbers in the INSTRUCTOR table
have been entered in the (###)###-#### format.
Solution:
SELECT phone
FROM instructor
WHERE TRANSLATE(
phone, '0123456789',
'##########') = '(###)###-####'
no rows selected
You can optionally include an extra space after the '9', which will
ignore any extra spaces added to the phone number. For example,
numbers in the format (212) 555-1111 and (212)555-1111 would be
listed in the result set. In the case of the INSTRUCTOR table, all the
phone numbers do not follow this format; therefore no rows are shown
in the output.
SELECT phone, instructor_id
FROM instructor
WHERE TRANSLATE(
phone, '0123456789 ',
'##########') = '(###)###-####'
no rows selected

Refer to Chapter 16, “Regular Expressions and Hierarchical Queries,”
for more advanced format checking using regular expressions.
5. Explain the functionality of the following query.
SELECT section_id, capacity,
CASE WHEN MOD (capacity, 2) <> 0 THEN 'Odd capacity'
ELSE 'Even capacity'
END "Odd or Even"
FROM section
WHERE section_id IN (101, 146, 147)
Solution: The query shows for sections 101, 146, and 147 the
SECTION_ID and CAPACITY in the first two columns. The last column
displays either the words 'Even capacity' or 'Odd capacity' depending
on the value of the capacity.
SECTION_ID CAPACITY Odd or Even
---------- ---------- -------------
101 10 Even capacity
146 25 Odd capacity
147 15 Odd capacity
3 rows selected.

Chapter 5: Date and Conversion Functions
1. Display all the sections where classes start at 10:30 AM.
Solution:
SELECT section_id, TO_CHAR(start_date_time, 'HH24:MI')
FROM section
WHERE TO_CHAR(start_date_time, 'HH24:MI') ='10:30'
SECTION_ID TO_CH
---------- -----
85 10:30
95 10:30
104 10:30
109 10:30
116 10:30
122 10:30
6 rows selected.
2. Write a query that accomplishes the following result. The output
shows you all the days of the week where sections 99, 89, and 105
start. Note the order of the days.
DAY SECTION_ID
--- ----------
Mon 99
Tue 89
Wed 105
3 rows selected.
Solution:
SELECT TO_CHAR(start_date_time, 'Dy') day, section_id
FROM section
WHERE section_id IN (99,89,105)
ORDER BY TO_CHAR(start_date_time, 'D')
The 'Dy' format displays the days as Mon, Tues, and so forth. The 'D'
format listed in the ORDER BY clause will return '1' for Sunday, '2' for
Monday, '3' for Tuesday, etc. The 'D' format in the ORDER BY clause
is preferable if you want to order not alphabetically but by the day of
the week. In this particular example, the alphabetical ordering of the
days coincides with the sequence of days of the week, but there may

be instances where this is not the case. Therefore, the 'D' format is
preferable if that's the desired ordering.
3. Select the distinct course costs for all the courses. If a course cost
is unknown, substitute a zero. Format the output with a leading $ sign,
and separate the thousands with a comma. Display two digits after the
decimal point. The query's output should look like the following result.
COST
-----------
$0.00
$1,095.00
$1,195.00
$1,595.00
4 rows selected.
Solution:
SELECT DISTINCT TO_CHAR(NVL(cost, 0), '$99,990.99') cost
FROM course
ORDER BY cost
or:
SELECT DISTINCT TO_CHAR(COALESCE(cost, 0), '$99,990.99')
cost
FROM course
ORDER BY cost
4. List all the rows of the GRADE_TYPE table that were created in the
year 1998.
Solution:
SELECT *
FROM grade_type
WHERE created_date >=TO_DATE('01-JAN-1998', 'DD-MON-YYYY')
AND created_date < TO_DATE('01-JAN-1999', 'DD-MON-YYYY')
5. What, if anything, is wrong with the following SQL statement?
SELECT zip + 100
FROM zipcode
Solution: The query executes, but doesn't make sense because you
don't do calculations on the ZIP column, that's one of the reasons why
the ZIP column in VARCHAR2 data type format and it stores leading
zeros. Additionally, any calculation should not rely on an implicit
conversion; it is better to use the TO_NUMBER function.

6. For the students enrolled on January 30, 2007, display the columns
STUDENT_ID and ENROLL_DATE.
Solution: There are many possible solutions, here are just a few listed:
SELECT student_id, enroll_date
FROM enrollment
WHERE enroll_date> = TO_DATE('30-JAN-2007', 'DD-MON-YYYY')
AND enroll_date < TO_DATE('31-JAN-2007', 'DD-MON-YYYY')
or:
FROM enrollment
WHERE enroll_date >= DATE '2007-01-30'
AND enroll_date < DATE '2007-01-31'
or:
FROM enrollment
WHERE TRUNC(enroll_date) = TO_DATE('30-JAN-2007', 'DD-MON-
YYYY')
Resulting output:
STUDENT_ID ENROLL_DA
---------- ---------
102 30-JAN-07
102 30-JAN-07
103 30-JAN-07
104 30-JAN-07
105 30-JAN-07
106 30-JAN-07
106 30-JAN-07
107 30-JAN-07
108 30-JAN-07
109 30-JAN-07
109 30-JAN-07
11 rows selected.

Chapter 6: Aggregate Functions, GROUP
BY and HAVING
1. List the order in which the WHERE, GROUP BY, and HAVING clauses
are executed by the database in the following SQL statement.
SELECT section_id, COUNT(*), final_grade
FROM enrollment
WHERE TRUNC(enroll_date) > TO_DATE('2/16/2003', 'MM/DD/YYYY')
GROUP BY section_id, final_grade HAVING COUNT(*) > 5
Solution: First the WHERE clause is executed, then the GROUP BY, and
lastly the HAVING clause is applied.
2. Display a count of all the different course costs in the COURSE
table.
Solution:
SELECT cost, COUNT(*)
FROM course
GROUP BY cost
COST COUNT(*)
--------- ---------
1095 3
1195 25
1595 1
1
4 rows selected.
Note the NULL value in the result set, and notice the difference if you
write the SQL statement using COUNT(cost)instead.
SELECT cost, COUNT(cost)
FROM course
GROUP BY cost
COST COUNT(COST)
--------- -----------
1095 3
1195 25
1595 1
0
4 rows selected.

3. Determine the number of students living in zip code 10025.
Solution:
SELECT COUNT(*)
FROM student
WHERE zip = '10025'
COUNT(*)
---------
3
1 row selected.
4. Show all the different companies for which students work. Display
only companies in which more than four students are employed.
Solution:
SELECT employer, COUNT(*)
FROM student
GROUP BY employer
HAVING COUNT(*) > 4
EMPLOYER COUNT(*)
-------------------- ---------
Amer.Legal Systems 10
Crane Co. 6
Electronic Engineers 15
New York Pop 8
4 rows selected.
5. List how many sections each instructor teaches.
Solution:
SELECT instructor_id, COUNT(*)
FROM section
GROUP BY instructor_id
INSTRUCTOR_ID COUNT(*)
------------- ---------
101 9
102 10
103 10
104 10
105 10
106 10
107 10
108 9

8 rows selected.
6. What problem does the following statement solve?
SELECT COUNT(*), start_date_time, location
FROM section
GROUP BY start_date_time, location
HAVING COUNT(*) > 1
Solution:
List the date, time, and location of sections that meet at the same
time, date, and location.
COUNT(*) START_DAT LOCATION
-------- --------- --------
2 09-APR-07 L214
2 16-APR-07 L509
2 rows selected.
7. Determine the highest grade achieved for the midterm within each
section.
Solution:
SELECT section_id, MAX(numeric_grade)
FROM grade
WHERE grade_type_code = 'MT'
GROUP BY section_id
SECTION_ID MAX(NUMERIC_GRADE)
---------- ------------------
80 76
81 88
...
154 92
156 99
56 rows selected.
8. Suppose you have a table called CUSTOMER_ORDER, which
contains 5,993 rows with an order total of $10,993,333.98 based on
the orders from 4,500 customers. Given this scenario, how many
row(s) does the following query return?
SELECT SUM(order_amount) AS "Order Total"
FROM customer_order
Solution: Aggregate functions always return a single row. The result of
the SUM function will return 10,993.333.98.

Chapter 7: Equijoins
1. Select the course description, section number, and location for
sections meeting in location L211.
Solution:
SELECT description, section_no, location
FROM course c, section s
WHERE c.course_no = s.course_no
AND location = 'L211'
Using the ANSI JOIN syntax and the ON clause, it can also be written
as:
FROM course c JOIN section s
ON c.course_no = s.course_no
WHERE location = 'L211'
Or with the USING clause:
USING (course_no)
DESCRIPTION SECTION_NO LOCAT
--------------------------------- ---------- -----
Project Management 1 L211
Java Developer I 4 L211
Intermediate Java Programming 2 L211
3 rows selected.
2. Show the course description, section number, starting date and
time of the courses Joseph German is taking.
Solution:
SELECT description, section_no, start_date_time
FROM course c, section s, enrollment e, student st
AND s.section_id = e.section_id
AND e.student_id = st.student_id
AND st.last_name = 'German'
AND first_name = 'Joseph'
DESCRIPTION SECTION_NO START_DAT
------------------------- ---------- ---------
Intro to Java Programming 2 24-JUL-07

1 row selected.
As always you can express this with the ANSI join syntax as follows
which may look like this:
SELECT c.description, s.section_no,
TO_CHAR(s.start_date_time, 'DD-MON-YYYY HH24:MI:SS')
ON (c.course_no = s.course_no)
JOIN enrollment e
ON (s.section_id = e.section_id)
JOIN student st
ON (e.student_id = st.student_id)
WHERE st.last_name = 'German'
AND st.first_name = 'Joseph'
Or you can write as follows with the USING clause.
SELECT c.description, s.section_no,
TO_CHAR(s.start_date_time, 'DD-MON-YYYY HH24:MI:SS')
USING (course_no)
JOIN enrollment e
USING (section_id)
JOIN student st
USING (student_id)
WHERE st.last_name = 'German'
AND st.first_name = 'Joseph'
3. List the instructor ID, last name of the instructor, and section ID of
sections where class participation contributes to 25 percent of the total
grade. Order the result by the instructor's last name.
Solution:
SELECT i.instructor_id, s.section_id, last_name
FROM instructor i, section s, grade_type_weight w
WHERE i.instructor_id = s.instructor_id
AND s.section_id = w.section_id
AND percent_of_final_GRADE = 25
AND grade_type_code = 'PA'
ORDER BY last_name
INSTRUCTOR_ID SECTION_ID LAST_NAME
------------- ---------- ----------
107 115 Frantzen
101 133 Hanks
108 155 Lowry

105 129 Morris
105 144 Morris
104 82 Pertez
106 137 Smythe
102 149 Wojick
102 88 Wojick
9 rows selected.
Or as an ANSI join with the USING clause:
SELECT instructor_id, section_id, last_name
FROM instructor JOIN section
USING (instructor_id)
JOIN grade_type_weight
USING (section_id)
WHERE percent_of_final_grade = 25
AND grade_type_code = 'PA'
ORDER BY 3
4. Display the first and last names of students who received 99 or
more points on the class project.
Solution:
SELECT first_name, last_name, numeric_grade
FROM student s, enrollment e, grade g
WHERE s.student_id = e.student_id
AND e.student_id = g.student_id
AND e.section_id = g.section_id
AND numeric_grade >= 99
AND grade_type_code = 'PJ'
FIRST_NAME LAST_NAME NUMERIC_GRADE
---------- --------------- -------------
May Jodoin 99
Joel Brendler 99
2 rows selected.
Or as expressed with an ANSI join:
SELECT first_name, last_name, numeric_grade
FROM student JOIN enrollment
USING (student_id)
JOIN grade
USING (student_id, section_id)
WHERE numeric_grade >= 99
AND grade_type_code = 'PJ'

5. Select the grades for quizzes of students living in zip code 10956.
Solution:
SELECT s.student_id, s.last_name, s.first_name,
g.numeric_grade, s.zip
FROM student s, enrollment e, grade g
AND e.section_id = g.section_id
AND g.grade_type_code = 'QZ'
AND s.zip = '10956'
STUDENT_ID LAST_NAME FIRST_NAME NUMERIC_GRADE ZIP
---------- ----------- ----------- ------------- -----
193 Jamerncy Al 91 10956
193 Jamerncy Al 90 10956
2 rows selected.
Alternatively, you can also join the GRADE table directly to the
STUDENT table. (For more information on skipping this table, see Lab
7.2 and the paragraph titled "SKIPPING THE PRIMARY/FOREIGN KEY
PATH"
FROM student s, grade g
WHERE g.grade_type_code = 'QZ'
AND g.student_id = s.student_id
AND s.zip = '10956'
Or expressed in ANSI join syntax with three tables:
FROM student s JOIN enrollment e
ON (s.student_id = e.student_id)
JOIN grade g
ON (e.student_id = g.student_id
AND e.section_id = g.section_id)
WHERE g.grade_type_code = 'QZ'
AND s.zip = '10956'
6. List the course number, section number, and instructor first and
last names of classes with course number 350 as a prerequisite.
Solution:
SELECT c.course_no, section_no, first_name,

last_name
FROM course c, section s, instructor i
AND s.instructor_id = i.instructor_id
AND prerequisite = 350
COURSE_NO SECTION_NO FIRST_NAME LAST_NAME
--------- ---------- ---------- -----------
450 1 Fernand Hanks
1 row selected.
The solution can also be achieved using one of the ANSI join syntax
variants:
SELECT c.course_no, section_no, first_name,
last_name
JOIN instructor i
ON (s.instructor_id = i.instructor_id)
WHERE prerequisite = 350
7. What problem do the following two SELECT statements solve?
SELECT stud.student_id, i.instructor_id,
stud.zip, i.zip
FROM student stud, instructor i
WHERE stud.zip = i.zip
SELECT stud.student_id, i.instructor_id,
stud.zip, i.zip
FROM student stud, enrollment e, section sec,
instructor i
WHERE stud.student_id = e.student_id
AND e.section_id = sec.section_id
AND sec.instructor_id = i.instructor_id
AND stud.zip = i.zip
Solution: The two queries identify students that live in the same zip
code as instructors.
The first statement determines those instructors who live in the same
zip code as students. It builds a Cartesian product, because there are
multiple occurrences of the same zip code in both the INSTRUCTOR
and STUDENT tables. The result looks like this:
STUDENT_ID INSTRUCTOR_ID ZIP ZIP

---------- ------------- ----- -----
223 102 10025 10025
399 102 10025 10025
163 102 10025 10025
223 103 10025 10025
399 103 10025 10025
163 103 10025 10025
223 106 10025 10025
399 106 10025 10025
163 106 10025 10025
223 108 10025 10025
399 108 10025 10025
163 108 10025 10025
12 rows selected.
The second statement shows the instructors who live in the same zip
code as the student they teach. The result is as follows:
STUDENT_ID INSTRUCTOR_ID ZIP ZIP
---------- ------------- ----- -----
223 103 10025 10025
163 106 10025 10025
2 rows selected.

Chapter 8: Subqueries
1. Using a subquery construct, determine which sections the
student Henry Masser is enrolled in.
Solution:
SELECT section_id
FROM enrollment
WHERE student_id IN
(SELECT student_id
FROM student
WHERE last_name = 'Masser'
AND first_name = 'Henry')
no rows selected
Note: Henry Masser is not enrolled in any section at all. The query
returns no rows.
2. What problem does the following SELECT statement solve?
SELECT zip
FROM zipcode z
WHERE NOT EXISTS
(SELECT '*'
FROM student
WHERE z.zip = zip)
AND NOT EXISTS
(SELECT '*'
FROM instructor
WHERE z.zip = zip)
Solution: The query determines the zip codes not found in either the
STUDENT table or the INSTRUCTOR table.
3. Display the course number and description of courses with no
enrollment. Also include courses which have no section assigned.
Solution:
SELECT course_no, description
FROM course c
WHERE NOT EXISTS
(SELECT NULL
FROM section s
WHERE c.course_no = s.course_no)
OR course_no IN
(SELECT course_no
FROM section s2

WHERE NOT EXISTS
(SELECT NULL
FROM enrollment e
WHERE s2.section_id = e.section_id))
COURSE_NO DESCRIPTION
--------- ---------------------------------
25 Intro to Programming
80 Programming Techniques
...
350 Java Developer II
430 Java Developer III
16 rows selected.
4. Can the ANY and ALL operators be used on the DATE data type?
Write a simple query to prove your answer.
Solution: Yes, the ANY and ALL operators work on the DATE data type.
There are many different possible sample queries. Here is one for each
operator. The queries produce the correct result with no error.
SELECT 'Hello'
FROM dual
WHERE TO_DATE('12-MAR-2009', 'DD-MON-YYYY') < ANY
(TO_DATE('13-MAR-2009', 'DD-MON-YYYY'),
TO_DATE('14-MAR-2009', 'DD-MON-YYYY'))
'HELL
-----
Hello
1 row selected.
SELECT 'Hello again'
FROM dual
WHERE TO_DATE('12-MAR-2096', 'DD-MON-YYYY') >ALL
(SELECT created_date
FROM grade)
'HELLOAGAIN
-----------
Hello again
1 row selected.
5. If you have a choice to write either a correlated subquery or a
simple subquery, which one would you choose? Why?
Solution:

The correlated subquery using the NOT EXISTS operator tests for NULL
values which the NOT IN operator does not. Another consideration is
the number of records returned by the outer query and the inner
query. If the outer query returns a large number of records, the
correlated subquery must test for each of these outer rows, which is
very time-consuming. If the inner query returns only a very few
records, the simple subquery is typically best. To determine the most
efficient statement, test against realistic data volumes and properly
indexed tables. For more information about this topic see Chapter 18,
"SQL Optimization."
6. Determine the top three zip codes where most of the students
live.
Solution:
SELECT s.*, ROWNUM ranking
FROM (SELECT zip, COUNT(*)
FROM student
GROUP BY zip
ORDER BY 2 DESC) s
WHERE ROWNUM <= 3
ZIP COUNT(*) RANKING
----- --------- ---------
07024 9 1
07010 6 2
11368 6 3
3 rows selected.
Note, if you execute the inline view query, you notice that there are
actually three zip codes with six students enrolled each. Below is a
partial listing of the query.
SELECT zip, COUNT(*)
FROM student
GROUP BY zip
ORDER BY 2 DESC
ZIP COUNT(*)
----- ---------
07024 9
07010 6
11373 6
11368 6
07042 5
...
06605 1

06798 1
145 rows selected.
The zip code 07024 has the largest number of students. Three zip
codes follow with an equal number of enrollments. But only two are
included in the query, because the ROWNUM pseudocolumn picks a
maximum of three rows. In Chapter 17, "Exploring Data Warehousing
Features," you will learn more about top-n queries.

Chapter 9: Set Operators
1. List all the zip codes in the ZIPCODE table that are not used in
the STUDENT or INSTRUCTOR tables. Write two different solutions,
using set operators for both.
Solution:
SELECT zip
FROM zipcode
MINUS
SELECT zip
FROM student
MINUS
SELECT zip
FROM instructor
or:
SELECT zip
FROM zipcode
MINUS
(SELECT zip
FROM student
UNION
SELECT zip
FROM instructor)
ZIP
-----
00914
06401
...
30342
33431
79 rows selected.
2. Write a SQL statement, using a set operator, to show which
students enrolled in a section on the same day they registered.
Solution:
SELECT student_id, TRUNC(registration_date)
FROM student
INTERSECT
SELECT student_id, TRUNC(enroll_date)
FROM enrollment
no rows selected

3. Find the students who are not enrolled in any classes. Write
three solutions: a set operation, a subquery, and a correlated
subquery.
Solution:
SELECT student_id
FROM student
MINUS
SELECT student_id
FROM enrollment
SELECT student_id
FROM student
WHERE student_id NOT IN
(SELECT student_id
FROM enrollment)
SELECT student_id
FROM student s
WHERE NOT EXISTS
(SELECT 'x'
FROM enrollment e
WHERE s.student_id = e.student_id)
STUDENT_ID
----------
284
285
...
397
399
103 rows selected.
4. Show the students who have received grades for their class.
Write four solutions: a set operation, a subquery, a correlated
subquery, and a join.
Solution:
SELECT section_id, student_id
FROM enrollment
INTERSECT
FROM grade
FROM enrollment

WHERE (student_id, section_id) IN
(SELECT student_id, section_id
FROM grade)
FROM enrollment e
WHERE EXISTS
(SELECT 1
FROM grade g
WHERE e.section_id = g.section_id
AND e.student_id = g.student_id)
SELECT DISTINCT e.section_id, e.student_id
FROM enrollment e, grade g
WHERE e.section_id = g.section_id
SECTION_ID STUDENT_ID
---------- ----------
80 128
81 103
...
156 214
156 215
226 rows selected.

Chapter 10: Complex Joins
1. Write a query that shows all the instructors who live in the same
zip code.
Solution:
SELECT DISTINCT i1.first_name, i1.last_name, i1.zip
FROM instructor i1, instructor i2
WHERE i1.zip = i2.zip
AND i1.instructor_id <> i2.instructor_id
ORDER BY i1.zip
FIRST_NAME LAST_NAME ZIP
---------- --------------- -----
Rick Chow 10015
Fernand Hanks 10015
Anita Morris 10015
Charles Lowry 10025
Nina Schorin 10025
Todd Smythe 10025
Tom Wojick 10025
7 rows selected.
Or the query can also be written as an ANSI join as follows:
SELECT DISTINCT i1.first_name, i1.last_name, i1.zip
FROM instructor i1 JOIN instructor i2
ON (i1.zip = i2.zip)
WHERE i1.instructor_id <> i2.instructor_id
ORDER BY i1.zip
Note: You can also move the WHERE conditions into the ON clause and
it will yield the same result as they are all AND conditions that need to
be met for the records to be returned in the result set.
2. Are any of the rooms overbooked? Determine whether any
sections meet at the same date, time, and location.
Solution:
SELECT DISTINCT s.section_id,
TO_CHAR(s.start_date_time, 'DD-MON-YYYY HH24:MI'),
s.location
FROM section s, section b
WHERE s.location = b.location
AND s.start_date_time = b.start_date_time

AND s.section_id <> b.section_id
ORDER BY 2, 3
SECTION_ID TO_CHAR(S.START_D LOCAT
---------- ----------------- -----
128 09-APR-2007 09:30 L214
132 09-APR-2007 09:30 L214
101 16-APR-2007 09:30 L509
140 16-APR-2007 09:30 L509
4 rows selected.
Instead of using the primary key to compare if this is the same row or
not, you could use the ROWID pseudocolumn instead (see Chapter 13,
“Indexes, Sequences, and Views” for more on ROWIDs). The ROWID
can be useful if no primary key on table exists.
WHERE s.location = b.location
AND s.start_date_time = b.start_date_time
AND s.rowid <> b.rowid
Alternatively, the query can be written as follows:
SELECT section_id, TO_CHAR(start_date_time,
'DD-MON-YYYY HH24:MI'), location
FROM section
WHERE (location, start_date_time) IN
(SELECT location, start_date_time
FROM section
GROUP BY start_date_time, location
HAVING COUNT(*) > 1)
3. Determine whether there is any scheduling conflict between
instructors: Are any instructors scheduled to teach one or more
sections at the same date and time? Order the result by the
INSTRUCTOR_ID and the starting date and time of the sections.
Solution:
SELECT DISTINCT s1.instructor_id,
TO_CHAR(s1.start_date_time, 'DD-MON-YYYY HH24:MI'),
s1.section_id
FROM section s1, section s2
WHERE s1.instructor_id = s2.instructor_id
AND s1.start_date_time = s2.start_date_time
AND s1.section_id <> s2.section_id
INSTRUCTOR_ID TO_CHAR(S1.START_ SECTION_ID
------------- ----------------- ----------
101 16-APR-2007 09:30 101
101 16-APR-2007 09:30 140
102 04-MAY-2007 09:30 88

102 04-MAY-2007 09:30 149
103 14-JUL-2007 09:30 107
103 14-JUL-2007 09:30 119
103 15-MAY-2007 09:30 89
103 15-MAY-2007 09:30 150
103 24-JUL-2007 09:30 81
103 24-JUL-2007 09:30 127
103 24-JUL-2007 09:30 142
104 12-JUN-2007 09:30 90
104 12-JUN-2007 09:30 151
105 07-MAY-2007 09:30 97
105 07-MAY-2007 09:30 129
107 07-MAY-2007 09:30 99
107 07-MAY-2007 09:30 115
107 21-MAY-2007 09:30 138
107 21-MAY-2007 09:30 154
108 09-JUN-2007 09:30 100
108 09-JUN-2007 09:30 139
21 rows selected.
Alternatively, you can write the SQL statement as follows:
SELECT instructor_id, start_date_time, section_id
FROM section
WHERE (instructor_id, start_date_time) IN
(SELECT instructor_id, start_date_time
FROM section
GROUP BY instructor_id, start_date_time
HAVING COUNT(*) > 1)
4. Show the course number, description, course cost, and section
ID for courses that cost 1195 or more. Include courses that have no
corresponding section.
Solution:
SELECT c.course_no, description, section_id, cost
FROM course c LEFT OUTER JOIN section s
WHERE cost >= 1195
ORDER BY 1
COURSE_NO DESCRIPTION SECTION_ID COST
--------- ------------------------- ---------- ---------
10 Technology Concepts 80 1195
...
80 Programming Techniques 1595
100 Hands-On Windows 141 1195
...

124 Advanced Java Programming 126 1195
124 Advanced Java Programming 127 1195
...
430 Java Developer III 1195
71 rows selected.
Note courses 80 and 430 do not have a corresponding section
assigned.
Or you can write the query using the traditional syntax, with the
comma between the tables in the FROM clause.
SELECT c.course_no, description, section_id, cost
FROM course c, section s
WHERE c.course_no = s.course_no(+)
AND cost >= 1195
ORDER BY 1
5. Write a query that lists the section numbers and students IDs of
students enrolled in classes held in location 'L210'. Include sections for
which no students are enrolled.
Solution:
SELECT s.section_id, e.section_id, e.student_id
FROM section s LEFT OUTER JOIN enrollment e
ON s.section_id = e.section_id
SECTION_ID SECTION_ID STUDENT_ID
---------- ---------- ----------
81 81 103
81 81 104
81 81 240
84 84 158
...
124
129
...
155 155 248
155 155 241
155 155 127
31 rows selected.
You can also write the query as follows:
SELECT s.section_id, e.section_id, e.student_id
FROM section s, enrollment e
AND s.section_id = e.section_id(+)

Chapter 11: Insert, Update, and Delete
1. Write and execute two INSERT statements to insert rows in the
ZIPCODE table for the following two cities: Newton, MA 02199 and
Cleveland, OH 43011. After your INSERT statements are successful,
make the changes permanent.
Solution:
INSERT INTO zipcode
(city, state, zip, created_date, created_by,
modified_date, modified_by)
VALUES
('Newton', 'MA', '02199', SYSDATE, USER,
SYSDATE, USER)
INSERT INTO zipcode
(city, state, zip, created_date, created_by,
modified_date, modified_by)
VALUES
('Cleveland', 'OH', '43011', SYSDATE, USER,
SYSDATE, USER)
COMMIT
2. Make yourself a student by writing and executing an INSERT
statement to insert a row into the STUDENT table with data about you.
Use one of the zip codes you inserted in exercise 1. Insert values into
the columns STUDENT_ID (use the value of '900'), FIRST_NAME,
LAST_NAME, ZIP, REGISTRATION_DATE (use a date that is five days
after today), CREATED_BY, CREATED_DATE, MODIFIED_BY, and
MODIFIED_DATE. Issue a COMMIT command when you are done.
Solution:
INSERT INTO student
(student_id, first_name, last_name,
zip, registration_date,
created_by, created_date, modified_by, modified_date)
VALUES
(900, 'Sandy', 'Dellacorte',
'02199', SYSDATE + 5,
USER, SYSDATE, USER, SYSDATE)
COMMIT
3. Write an UPDATE statement to update the data about you in the
STUDENT table. Update the columns SALUTATION, STREET_ADDRESS,

PHONE, and EMPLOYER. Be sure to also update the MODIFIED_DATE
column and make the changes permanent.
Solution:
UPDATE student
SET salutation = 'Ms.',
street_address = '60 Winter St.',
phone = '617-236-2746',
employer = 'Raytone',
modified_by = USER,
modified_date = SYSDATE
WHERE student_id = 900
COMMIT
4. Delete the row you created the STUDENT table and the two rows
you created in the ZIPCODE table. Be sure to issue a COMMIT
command afterwards. . You can perform this action by using a SQL
command or SQL Developer’s Data tab.
Solution:
DELETE FROM student
DELETE FROM zipcode
WHERE zip IN ('02199', '43011')
COMMIT
5. Delete the zip code 10954 from the ZIPCODE table by using SQL
Developer. Commit your change after you delete the row. Describe
the results of your actions.
Solution: SQL Developer marks the row for deletion upon pressing the
Delete icon. However, as soon as you commit the change, Oracle
recognizes that dependent records exist and disallows the deletion of
the row. The Data Editor Log tab reports the error as shown below.

If you performed the exercises in this chapter, you will have changed
data in most of the tables of the STUDENT schema. If you go back to the
previous chapters and reexecute those queries, you might find that the
results are different than they were before. Therefore, if you want to
reload the tables and data, you can run the rebuildStudent.sql script.

Chapter 12: Create, Alter, and Drop Tables
1. Create a table called TEMP_STUDENT with the following columns
and constraints: a column STUDID for student ID that is NOT NULL
and is the primary key, a column FIRST_NAME for student first name;
a column LAST_NAME for student last name, a column ZIP that is a
foreign key to the ZIP column in the ZIPCODE table, a column
REGISTRATION_DATE that is NOT NULL and has a CHECK constraint to
restrict the registration date to dates after January 1st, 2000.
Solution:
CREATE TABLE temp_student
(studid NUMBER(8) NOT NULL,
first_name VARCHAR2(25),
last_name VARCHAR2(25),
zip VARCHAR2(5),
registration_date DATE NOT NULL,
CONSTRAINT temp_student_pk PRIMARY KEY(studid),
CONSTRAINT temp_student_zipcode_fk FOREIGN KEY(zip)
REFERENCES zipcode(zip),
CONSTRAINT temp_student_reg_date_ck
CHECK(registration_date >
TO_DATE('01-JAN-2000', 'DD-MON-YYYY'))
)
2. Write an INSERT statement that violates one of the constraints
for the TEMP_STUDENT table you created in exercise 1. Write another
INSERT statement that succeeds when executed, and commit your
work.
Solution:
INSERT INTO temp_student
(studid, first_name, last_name,
zip, registration_date)
VALUES
(NULL, 'Alex', 'Morrison', '99999', TO_DATE('01-DEC-
1999', 'DD-MON-YYYY'))
*
ERROR at line 1:
ORA-01400: cannot insert NULL into
("STUDENT"."TEMP_STUDENT"."STUDID")

VALUES (101, 'Alex', 'Morrison', '07656', TO_DATE('01-DEC-
2000', 'DD-MON-YYYY'))
1 row created.
3. Alter the TEMP_STUDENT table to add two more columns called
EMPLOYER and EMPLOYER_ZIP. The EMPLOYER_ZIP column should
have a foreign key constraint that references the ZIP column of the
ZIPCODE table. Update the EMPLOYER column, and alter the table
once again to make the EMPLOYER column NOT NULL. Drop the
TEMP_STUDENT table when you are done with the exercise.
Solution:
ALTER TABLE temp_student
ADD (employer VARCHAR2(20),
employer_zip VARCHAR2(5),
CONSTRAINT temp_student_fk
FOREIGN KEY(employer_zip)
REFERENCES zipcode(zip))
UPDATE temp_student
SET employer = 'ANM Productions'
ALTER TABLE temp_student
MODIFY (employer NOT NULL)
DROP TABLE temp_student

Chapter 13: Indexes, Sequences, and
Views
1. Who can update the SALARY column through the MY_EMPLOYEE
view? Hint: The USER function returns the name of the user who is
currently logged in.
CREATE OR REPLACE VIEW my_employee AS
SELECT employee_id, employee_name, salary, manager
FROM employee
WHERE manager = USER
WITH CHECK OPTION CONSTRAINT my_employee_ck_manager
Solution: Only managers can update their respective employee's
salaries. The WITH CHECK OPTION constraint ensures that DML
statements satisfy the condition in the WHERE clause. This condition
enforces that only records are displayed, updated, inserted, and
deleted where the value in the MANAGER column is equal to the user
currently logged in. A SELECT statement against the MY_EMPLOYEE
view for the user with the login ID of JONES could look like this:
EMPLOYEE_ID EMPLOYEE_NAME SALARY MANAG
----------- ------------------------- --------- -----
150 Gates 11787 JONES
251 Sheppard 11106 JONES
552 Edwards 7036 JONES
353 Philpotts 11373 JONES
2. Which columns in a table should you consider indexing?
Solution: Columns frequently used in the WHERE clause of SQL
statements are good candidates for indexes. Be sure to consider the
selectivity of the values of the columns, that is, how many distinct
values there are in the column. Sometimes it is useful to combine
several columns with a low selectivity in a concatenated index. Make
sure you properly access the index. You also see more examples on
indexes and their impact in Chapter 18, "SQL Optimization." In
addition, consider indexing foreign key columns, because they not only
are frequently referenced in the WHERE clause of joins, but also
improve the locking of records on the child table.
3. Explain the purpose of the Oracle SQL command below.
ALTER INDEX crse_crse_fk_i REBUILD

Solution: This command rebuilds an existing index named
CRSE_CRSE_FK_I without having to drop the old index first and then
re-create it.
4. Are NULLs stored in an index? Explain.
Solution: NULLs are not stored in an index. The exception is if it is a
concatenated index and the leading column of the index does not
contain a NULL value. Another exception is a bitmapped index, which
stores null values.

Chapter 14: The Data Dictionary,
Scripting, and Reporting
1. Describe the result of the following query.
SELECT table_name, column_name, comments
FROM user_col_comments
Solution:
Write a query to display all the column comments in the user's
schema.
TABLE_NAME COLUMN_NAME COMMENTS
---------- --------------- --------------------
COURSE COURSE_NO The unique ID for a
course.
COURSE DESCRIPTION The full name for th
is course.
...
ZIPCODE CREATED_DATE Audit column - indic
ates date of insert.
ZIPCODE MODIFIED_BY Audit column - indic
ates who made last u
pdate.
ZIPCODE MODIFIED_DATE Audit column - date
of last update.
122 rows selected.
The result of your query may vary from the above result depending on
the objects you have created. The result shows a list of column
comments. It is useful to place comments on columns and/or tables
describing the information found within the column or table. The
following command creates a column comment for the
INSTRUCTOR_ID column on the INSTRUCTOR table.
COMMENT ON COLUMN INSTRUCTOR.INSTRUCTOR_ID IS 'The unique
ID for an instructor.'
Comment created.
A table comment is stored in the data dictionary view
USER_TAB_COMMENTS. The next statement creates a table comment
for the instructor table.
COMMENT ON TABLE INSTRUCTOR IS 'Profile information for an
instructor.'
Comment created.

2. Explain the differences between the views USER_USERS,
ALL_USERS, and DBA_USERS.
Solution: The USER_USERS view shows information about the
currently logged in user. You see useful information such as the
default tablespace name and the temporary tablespace name as well
as the date the user was created. The ALL_USERS view shows a list of
all the users in the system and the date the user was created.
The DBA_USERS view displays all the users in the system. The
columns listed include the date the user was created, the default and
temporary tablespaces, and the encrypted password.
3. What are the underlying data dictionary views for the public
synonyms TABS and COLS?
Solution: The public synonyms are USER_TABLES and
USER_TAB_COLUMNS. The queries to determine this solution are:
SELECT synonym_name, table_name
FROM all_synonyms
WHERE synonym_name IN ('TABS', 'COLS')
SYNONYM_NAME TABLE_NAME
------------------------------ ----------------------------
TABS USER_TABLES
COLS USER_TAB_COLUMNS
2 rows selected.
You can also query the DICT view with this statement.
SELECT *
FROM dict
WHERE table_name IN ('TABS', 'COLS')
TABLE_NAME COMMENTS
----------------------- ------------------------------
COLS Synonym for USER_TAB_COLUMNS
TABS Synonym for USER_TABLES
2 rows selected.
4. Write a dynamic SQL script to drop all views in the STUDENT
schema. If there are no views, create some to test your script.
Solution: To create some views issue the following statements.
CREATE OR REPLACE VIEW view1_v AS
SELECT *

FROM student
CREATE OR REPLACE VIEW view2_v AS
SELECT *
FROM course
Now create a file with the following commands. Save the file.
SET ECHO OFF
REM File name: drop_view.sql
REM Purpose: Drop all the views in a user's schema.
REM Created: 17-Mar-2009 AR
REM Version: 1.0
SET PAGESIZE 0
SET LINESIZE 80
SET FEEDBACK OFF
SET TERM OFF
SPOOL drop_view.out
SELECT 'DROP VIEW '||view_name||' ;'
FROM user_views;
SPOOL OFF
SET PAGESIZE 24
SET LINESIZE 80
SET FEEDBACK ON
SET TERM ON
SET ECHO ON
@drop_view.out
Then execute the file from the SQL*Plus prompt with the @ command.
SQL>@drop_view.sql

Chapter 15: Security
To complete the exercises below, create a new user called SCHOOL
with the password program, and grant CONNECT and RESOURCE
privileges to it. Then log in as the STUDENT user.
-- Create SCHOOL user
CONN SYSTEM/manager
CREATE USER school IDENTIFIED BY program;
GRANT CONNECT, RESOURCE TO school;
1. Create two roles: REGISTRAR and INSTRUCTOR.
Solution: Make sure you have the CREATE ROLE system privilege,
otherwise you will not be able to create the roles.
CONN student/learn
CREATE ROLE registrar;
CREATE ROLE instructor;
2. Create a view called CURRENT_REGS that reflects all students
who registered on January 25, 2007. Grant SELECT privileges on the
new view to the REGISTRAR role.
Solution:
CREATE OR REPLACE VIEW current_regs AS
SELECT first_name, last_name
FROM student
WHERE registration_date >= TO_DATE('25-JAN-2007', 'DD-MON-YYYY')
AND registration_date < TO_DATE('26-JAN-2007', 'DM-MON-YYYY');
GRANT SELECT ON current_regs TO registrar;
3. Create a view called roster that reflects all students taught by
the instructor Marilyn Frantzen. Grant SELECT privileges on the new
view to the INSTRUCTOR role.
Solution:
CREATE OR REPLACE VIEW roster AS
SELECT se.course_no course, se.section_id section,
s.first_name first, s.last_name last,
e.student_id
FROM student s, enrollment e, section se, instructor i
AND e.section_id = se.section_id
AND se.instructor_id = i.instructor_id
AND i.first_name = 'Marilyn'

AND i.last_name = 'Frantzen';
GRANT SELECT ON roster TO instructor;
4. Grant the REGISTRAR and INSTRUCTOR roles to the new user
called SCHOOL.
Solution:
GRANT registrar, instructor TO school;
5. Log in as the user SCHOOL and select from the two previously
created views.
Solution:
CONNECT school/program
SELECT *
FROM student.current_regs;
SELECT *
FROM student.roster;

Chapter 16: Regular Expressions and
Hierarchical Queries
1. Name other hierarchical relationships you are familiar with.
Solution: Examples of hierarchical relationships are a parts explosion,
also referred to as bill of materials, where you show all the parts that
go into the assembly of a final product. Another example is the
hierarchy of an organization, showing all the employees and their
respective managers. A financial profit and loss statement report can
be another example of a tree, where summary accounts are made up
of other summary accounts that finally result in posting-level accounts.
2. Change the prerequisite of course number 310 Operating
Systems, a root row in the hierarchy, from a null value to 145 Internet
Protocols. Write the query to detect the loop in the hierarchy, using
the CONNECT_BY_ISCYCLE pseudocolumn.
Solution: Without the change, the hierarchy for course number 310
looks like this:
310 Operating Systems
130 Intro to Unix
132 Basics of Unix Admin
134 Advanced Unix Admin
135 Unix Tips and Techniques
330 Network Administration
145 Internet Protocols
The UPDATE statement will create a loop in the hierarchy.
UPDATE course
SET prerequisite = 145
WHERE course_no = 310
Essentially, the CONNECT_BY_ISCYCLE returns the value of 1 if a row
has a child which is its own ancestor. The next query detects the loop.
SELECT *
FROM (SELECT course_no, prerequisite,
SYS_CONNECT_BY_PATH(course_no, '/') AS
"Path",
LEVEL, CONNECT_BY_ISCYCLE AS cycle

FROM course
CONNECT BY NOCYCLE PRIOR course_no = prerequisite)
WHERE cycle = 1
COURSE_NO PREREQUISITE Path LEVEL CYCLE
--------- ------------ --------------- ----- -----
145 310 /310/145 2 1
310 145 /145/310 2 1
2 rows selected.
If the loop is buried deeper in the hierarchy, your query will return
multiple rows that all indicate the loop being caused. For simple
checking of the hierarchy, it can be helpful to display the course
description such as SYS_CONNECT_BY_PATH(description, '*').
Be sure to reset the data back to its original state with this statement.
UPDATE course
SET prerequisite = NULL
WHERE course_no = 310
COMMIT
3. Why doesn’t this query return any rows?
SELECT *
FROM instructor
WHERE REGEXP_LIKE(instructor_id, '[:digit:]')
no rows selected
Solution: The REGEXPR_LIKE function does not recognize this pattern
as a character class [:digit:] because it is not enclosed with an extra
set of square brackets for the character class list.
4. Add a Social Security number column to the STUDENT table or
create a separate table with this column. Write a column check
constraint that verifies that the social security number is entered in the
correct ###-##-#### format.
Solution:
ALTER TABLE student
ADD (ssn VARCHAR2(11))
ALTER TABLE student

ADD CONSTRAINT stud_ssn_ck CHECK
(REGEXP_LIKE(ssn,
'^([[:digit:]]{3}-[[:digit:]]{2}-[[:digit:]]{4})$'))

Chapter 17: Exploring Data Warehousing
Features
1. Write the question for the following query and answer.
SELECT COUNT(DECODE(SIGN(total_capacity-20),
-1, 1, 0, 1)) "<=20",
COUNT(DECODE(SIGN(total_capacity-21),
0, 1, -1, NULL,
DECODE(SIGN(total_capacity-30), -1, 1)))
"21-30",
COUNT(DECODE(SIGN(total_capacity-30), 1, 1)) "31+"
FROM (SELECT SUM(capacity) total_capacity, course_no
FROM SECTION
GROUP BY COURSE_NO)
<=20 21-30 31+
--------- --------- ---------
2 10 16
1 row selected.
Solution: The question should be similar to one of the following:
Determine the total capacity for each course and order them in three
columns. List the number of courses with a total capacity of 20 or less
in one column, the number of courses with a total capacity between 21
and 30 in another, and lastly show the number of courses with a
capacity of over 31 in the third column. The result shows that there
are two courses with a total capacity of 20 or less, 10 courses with a
capacity between 21 and 30, and 16 courses with a capacity over 31
students.
2. Using an analytical function, determine the top three zip codes
where most of the students live.
Solution:
SELECT *
FROM (SELECT zip, COUNT(*),
DENSE_RANK() OVER(ORDER BY
COUNT(zip) DESC) AS rank
FROM student
GROUP BY zip)
WHERE rank <=3
ZIP COUNT(*) RANK
----- ---------- ----------
07024 9 1

07010 6 2
11373 6 2
11368 6 2
07042 5 3
11355 5 3
11209 5 3
07047 5 3
11375 5 3
11372 5 3
10 rows selected.
3. Explain the result of the following query.
SELECT 'Q'||TO_CHAR(start_date_time, 'Q') qtr,
TO_CHAR(start_date_time, 'DY') day, COUNT(*),
DENSE_RANK() OVER (
PARTITION BY 'Q'||TO_CHAR(start_date_time, 'Q')
ORDER BY COUNT(*) DESC) rank_qtr,
DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) rank_all
FROM enrollment e, section s
WHERE s.section_id = e.section_id
GROUP BY 'Q'||TO_CHAR(start_date_time, 'Q'),
TO_CHAR(start_date_time, 'DY')
ORDER BY 1, 4
QT DAY COUNT(*) RANK_QTR RANK_ALL
--- --- ---------- -------- ----------
Q2 MON 42 1 1
Q2 TUE 35 2 2
Q2 SAT 30 3 3
Q2 SUN 29 4 4
Q2 WED 15 5 6
Q2 FRI 13 6 7
Q2 THU 13 6 7
Q3 SAT 29 1 4
Q3 TUE 20 2 5
9 rows selected
Solution: The query generates a listing that shows the starting
quarter, day of the week of any sections and within the respective
quarter the number of enrollments. The RANK_QTR column indicates
ranking of the enrollment number of each quarter and the RANK_ALL
column shows the ranking for all time periods.

Chapter 18: SQL Optimization
1. Given the following execution plan, describe the steps and their
order of execution.
SELECT c.course_no, c.description,
i.instructor_id
FROM course c, section s, instructor i
WHERE prerequisite = 30
AND c.course_no = s.course_no
AND s.instructor_id = i.instructor_id
-------------------------------------------------------
| Id | Operation | Name |
-------------------------------------------------------
| 0 | SELECT STATEMENT | |
| 1 | NESTED LOOPS | |
| 2 | NESTED LOOPS | |
| 3 | TABLE ACCESS BY INDEX ROWID| COURSE |
| 4 | INDEX RANGE SCAN | CRSE_CRSE_FK_I |
| 5 | TABLE ACCESS BY INDEX ROWID| SECTION |
| 6 | INDEX RANGE SCAN | SECT_CRSE_FK_I |
| 7 | INDEX UNIQUE SCAN | INST_PK |
-------------------------------------------------------
Solution: This is a three-table join of the COURSE, SECTION, and
INSTRUCTOR tables. The first step executed in the execution plan is
the access of the index CRSE_CRSE_FK_I. This index is based on the
PREREQUISITE column and, therefore, retrieves the ROWIDs of those
records that satisfy the condition WHERE prerequisite = 30. Then the
rows with these ROWIDs are retrieved from the COURSE table.
The next step is a nested loop join with the SECTION table. For each of
the retrieved COURSE rows, the index SECT_CRSE_FK_I is probed
based on join criteria of s.course_no = c.course_no. Lastly, this result
is now used for another nested loop join with the INSTRUCTOR index.
Note that the query only requires the use of the INSTRUCTOR_ID
column, which is also the only column in the SELECT list. Therefore,
only a lookup of the value in the index is required, not the
INSTRUCTOR table.
2. Describe the steps of the following execution plan.
UPDATE enrollment e
SET final_grade =
(SELECT NVL(AVG(numeric_grade),0)

FROM grade
WHERE e.student_id = student_id
AND e.section_id = section_id)
AND section_id = 2000
0 rows updated.
----------------------------------------------------
| Id | Operation | Name |
----------------------------------------------------
| 0 | UPDATE STATEMENT | |
| 1 | UPDATE | ENROLLMENT |
| 2 | INDEX UNIQUE SCAN | ENR_PK |
| 3 | SORT AGGREGATE | |
| 4 | TABLE ACCESS BY INDEX ROWID| GRADE |
| 5 | INDEX RANGE SCAN | GR_PK |
----------------------------------------------------
Solution: This SQL UPDATE statement is a correlated subquery. You
can generate explain plans for SQL statements other than SELECT
statements. The explain plan shows that the WHERE clause of the
UPDATE statement refers to the primary key columns of the
ENROLLMENT and GRADE tables to identify the rows and to determine
the final grade values.
The inner query utilizes the index GR_PK, the primary key index, and
accesses the GRADE table via the ROWID. Because the subquery
specifies the AVG function, the step SORT (AGGREGATE) is executed.
Note, you will not see a difference in the execution plan between a
correlated UPDATE statement and an UPDATE statement with a non-
correlated subquery. You need to keep in mind, however, that the
correlated update will repeatedly execute the inner query for every
row retrieved by the outer query. This is in contrast to the non-
correlated subquery that executes the inner query only once. The
correlated subquery combined with an UPDATE statement is a very
fast way to update data without having to write a program to compute
records for each step.
3. The following SQL statement has an error in the hint. Correct the
statement so Oracle can use the hint.
SELECT /*+ INDEX (student stu_pk) */ *
FROM student s
WHERE last_name = 'Smith'
Solution: The hint does not specify the table alias. When a table alias
is used in the statement, the hint needs to reference the alias

otherwise the hint is ignored. You correct the statement as follows.
Note that this is not a very good index choice for this query but just
illustrates how you can direct Oracle to use a specific index.
SELECT /*+ INDEX (s stu_pk) */ *
FROM student s
WHERE last_name = 'Smith'

Database solution by m.moses wills

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Database solution by m.moses wills