1. Chapter 4 Tutorial

2. Modeling Data Warehouse
A data warehouse is based on a multidimensional data model which views data in the form of a data cube
A data cube allows data to be modeled and viewed in multiple dimensions
Dimension tables
Fact table contains measures and keys to related dimension tables

3. Cont.
Star schema: A fact table in the middle connected to a set of dimension tables.
Snowflake schema: represents dimensional hierarchy by normalizing the dimension tables.
save storage
reduces the effectiveness of browsing
Fact constellations: Multiple fact tables share dimension tables

4. OLAP Operations by climbing up hierarchy or by dimension reduction
Roll up (drill-up): summarize data
by climbing up hierarchy or by dimension reduction
Drill down (roll down): reverse of roll-up
from higher level summary to lower level summary or detailed data, or introducing new dimensions
Slice and dice:
project and select
Pivot (rotate):
reorient the cube, visualization, 3D to series of 2D planes

9. Q3
Suppose that a data warehouse consists of the three dimensions time, doctor, and patient, and the two measures count and charge, where charge is the fee that a doctor charges a patient for a visit.
(a) Enumerate three classes of schemas that are popularly used for modeling data warehouses.
Star schema
Snowflake schema
Fact constellation schema

10. Q3 cont.
(b) Draw a schema diagram for the above data warehouse using one of the schema classes listed in (a). Using a star schema.

11. Q3 cont. Star Schema time Fact Table Measures time_key doctor_id
day
day_of_the_week
month
quarter
year
time
doctor_id
doctor_name
phone #
address
gender
doctor
Fact Table
time_key
doctor_id
patient_id
Charge
Count
patient_id
patient_name
phone #
address
gender
patient
Measures

12. Q3 cont.
(c) Starting with the base cuboid [day, doctor, patient], what specific OLAP operations should be performed in order to list the total fee collected by each doctor in 2010?
The operations to be performed are:
Roll-up on time from day to year.
Slice for time = 2010.
Roll-up on patient from individual patient to all.

13. Q4
Suppose that a data warehouse for Big-University consists of the following four dimensions: student, course, semester, and instructor, and two measures count and avg. grade. When at the lowest conceptual level (e.g., for a given student, course, semester, and instructor combination), the avg grade measure stores the actual course grade of the student. At higher conceptual levels, avg grade stores the average grade for the given combination.

14. Q4 cont. Snowflake Schema
course_id
Course_name
department
Course
student_id
student_name
area_id
Major
status
university
Student
area_id
City
State
country
Area
Sales
Fact Table
course_id
student_id
instructor_id
semester_id
Count
Avg. grade
semester_id
semester
year
Semester
instructor_id
depatment
rank
Instructor

15. Q4. cont.
Starting with the base cuboid [student, course, semester, instructor], what specific OLAP operations (e.g., roll-up from semester to year) should one perform in order to list the average grade of CS courses for each Big University student.
Roll-up on course from course id to department.
Roll-up on semester from semester id to all.
Slice for course=“CS” .

16. Q5
Suppose that a data warehouse consists of the four dimensions, date, spectator, location, and game, and the two measures, count and charge, where charge is the fare that a spectator pays when watching a game on a given date. Spectators may be students, adults, or seniors, with each category having its own charge rate. Draw a star schema diagram for the data warehouse.

17. Q5 cont. Star Schema date Sales Fact Table date_id spectator_id
day
month
quarter
year
date
spectator_id
spectator_name
phone #
address
Status
Charge rate
spectator
Sales
Fact Table
date_id
spectator_id
location_id
game_id
Charge
Count
location_id
phone #
Street
city
province
country
location
game_id
game_name
description
producer
game

18. Q5. cont.
Starting with the base cuboid [date, spectator, location, game], what specific OLAP operations should one perform in order to list the total charge paid by student spectators at GM Place in 2010?
The specific OLAP operations to be performed are:
Roll-up on date from date id to year.
Roll-up on game from game id to all.
Roll-up on location from location id to location name.
Roll-up on spectator from spectator id to status.
Dice with status=“students”, location name=“GM Place”, and year = 2010.