1. EECS 647: Introduction to Database Systems
Instructor: Luke Huan
Spring 2007

2. Luke Huan Univ. of Kansas
Queries for Today
What is a database?
What is a database management system?
Why take a database course?
Who will teach?
How to take the class?
Preview of class contents
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Luke Huan Univ. of Kansas

3. What: Database Systems Then
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4. What: Database Systems Today
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5. What: Database Systems Today
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Luke Huan Univ. of Kansas

6. What: Database Systems Today
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7. Luke Huan Univ. of Kansas
So… What is a Database?
A database is a very large, integrated collection of data.
Data is a group of facts that can be recorded and have an implicit meaning.
Typically a database is used to model a real-world “enterprise” (or a miniworld)
Entities (e.g., basketball teams, games)
Relationships (e.g. KU’s basketball team won <you name it> last week)
Might surprise you how flexible this is
Web search:
Entities: words, documents
Relationships: word in document, document links to document.
P2P filesharing:
Entities: words, filenames, hosts
Relationships: word in filename, file available at host
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Luke Huan Univ. of Kansas

8. Main Characteristics of Databases
Self-describing nature of a database system
A DBMS catalog stores the description of the database. The description is called meta-data.
Insulation between programs and data
Allows changing data storage structures and operations without having to change the DBMS access
Data Abstraction
Use data model to hide storage details and present the users with a conceptual view of the database
Support of multiple views of the data
Each user may see a different view of the database, which describes only the data of interest to that user.
Sharing of data and multi-user transaction processing
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Luke Huan Univ. of Kansas

9. Databases make these folks happy ...
End users in many fields
Business, education, science, …
DB application programmers
Build data entry & analysis tools on top of DBMSs
Build web services that run off DBMSs
Database administrators (DBAs)
Design logical/physical schemas
Handle security and authorization
Data availability, crash recovery
Database tuning as needs evolve
DBMS vendors, programmers
Oracle, IBM, MS …
…must understand how a DBMS works
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10. What is a Database Management System?
A Database Management System (DBMS) is a collection of programs that enable uses to create and maintain databases
store, manage, and access data in a databases.
Typically this term is used narrowly
Relational databases with transactions
E.g. Oracle, DB2, SQL Server
Mostly because they predate other large repositories
Also because of technical richness
When we say DBMS in this class we will usually follow this convention
But keep an open mind about applying the ideas!
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Luke Huan Univ. of Kansas

11. Luke Huan Univ. of Kansas
What: Is the WWW a DBMS?
Fairly sophisticated search available
Crawler indexes pages on the web
Keyword-based search for pages
But, currently
data is mostly unstructured and untyped
search only:
can’t modify the data
can’t get summaries, complex combinations of data
few guarantees provided for freshness of data, consistency across data items, fault tolerance, …
web sites typically have a (relational) DBMS in the background to provide these functions.
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Luke Huan Univ. of Kansas

12. Luke Huan Univ. of Kansas
What: Is the WWW a DBMS?
The picture is changing quickly
Information Extraction to get structure from unstructured
New standards e.g., XML, Semantic Web can help data modeling
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Luke Huan Univ. of Kansas

13. What: “Search” vs. Query
What if you wanted to find out which actors donated to John Kerry’s presidential campaign?
Try “actors donated to john kerry” in your favorite search engine.
If it isn’t “published”, it can’t be searched!
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Luke Huan Univ. of Kansas

14. What: A “Database Query” Approach
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15. What: Is a File System a DBMS?
Thought Experiment 1:
You and your project partner are editing the same file.
You both save it at the same time.
Whose changes survive?
Q: How do you write programs over a subsystem when it promises you only “???” ?
A: Very, very carefully!!
A) Yours
B) Partner’s
C) Both
D) Neither
E) ???
Thought Experiment 2:
You’re updating a file.
The power goes out.
Which changes survive?
A) All
B) None
C) All Since Last Save
D) ???
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Luke Huan Univ. of Kansas

16. OS Support for Data Management
Data can be stored in RAM
this is what every programming language offers!
RAM is fast, and random access
Isn’t this heaven?
Every OS includes a File System
manages files on a magnetic disk
allows open, read, seek, close on a file
allows protections to be set on a file
drawbacks relative to RAM?
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Luke Huan Univ. of Kansas

17. Database Management Systems
What more could we want than a file system?
Simple, efficient ad hoc1 queries
concurrency control
recovery
benefits of good data modeling
S.M.O.P.2? Not really…
as we’ll see this semester
in fact, the OS often gets in the way!
1ad hoc: formed or used for specific or immediate problems or needs
2SMOP: Small Matter Of Programming
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Luke Huan Univ. of Kansas

18. Current Commercial Outlook
A major part of the software industry:
Oracle, IBM, Microsoft
also Sybase, Informix (now IBM), Teradata
smaller players: java-based dbms, devices, OO, …
Lots of related industries
data warehouse, document management, storage, backup, reporting, business intelligence, ERP, CRM, app integration
Traditional Relational DBMS products dominant and evolving
adapted for extensibility (user-defined types), native XML support.
Microsoft merger of file system/DB…?
Open Source coming on strong
MySQL, PostgreSQL, Apache Derby, BerkeleyDB, Ingres, EigenBase
And of course, the other “database” technologies
Search engines, P2P, etc.
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Luke Huan Univ. of Kansas

19. Advantages of a DBMS: a short list
Controlling redundancy
Restrict unauthorized access
Providing persistent storage for program objects
Providing storage structure for efficient query processing
Providing backup and crash recovery ….
And many many others that are going to be explored in this class
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Luke Huan Univ. of Kansas

20. What database systems will we cover?
We will be try to be broad and touch upon
Relational DBMS (e.g. Oracle, SQL Server, DB2, Postgres)
“Semi-structured” DB systems (e.g. XML repositories like Xindice)
Data mining: transfer data into knowledge!
Starting point
We assume you have used web search engines
We assume you don’t know relational databases
Yet they pioneered many of the key ideas
So focus will be on relational DBMSs
With frequent side-notes on search engines, XML issues
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Luke Huan Univ. of Kansas

21. Luke Huan Univ. of Kansas
Why take this class?
Database systems are at the core of CS
They are incredibly important to society
The topic is intellectually rich
It isn’t that much work
Looks good on your resume
Let’s spend a little time on each of these
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Luke Huan Univ. of Kansas

22. Luke Huan Univ. of Kansas
Why take this class?
A. Database systems are the core of CS
Shift from computation to information
True in corporate computing for years
Web, p2p made this clear for personal computing
Increasingly true of scientific computing
Need for DB technology has exploded in the last years
Corporate: retail swipe/clickstreams, “customer relationship mgmt”, “supply chain mgmt”, “data warehouses”, etc.
Web:not just “documents”. Search engines, e-commerce, blogs, wikis, other “web services”.
Scientific: digital libraries, genomics, satellite imagery, physical sensors, simulation data
Personal: Music, photo, & video libraries. archives. File contents (“desktop search”).
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Luke Huan Univ. of Kansas

23. Luke Huan Univ. of Kansas
Why take this class?
B. DBs are incredibly important to society
“Knowledge is power.” -- Sir Francis Bacon
“With great power comes great responsibility.” -- SpiderMan’s Uncle Ben
Policy-makers should understand technological possibilities.
Informed Technologists needed in public discourse on usage.
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Luke Huan Univ. of Kansas

24. Luke Huan Univ. of Kansas
Why take this class?
C. The topic is intellectually rich.
representing information
data modeling
languages and systems for querying data
complex queries & query semantics*
over massive data sets
concurrency control for data manipulation
controlling concurrent access
ensuring transactional semantics
reliable data storage
maintain data semantics even if you pull the plug
data mining
Let your data speak
* semantics: the meaning or relationship of meanings of a sign or set of signs
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Luke Huan Univ. of Kansas

25. Luke Huan Univ. of Kansas
Why take this class?
D. It isn’t that much work.
Bad news: It is a lot of work.
Good news: the course is front loaded
Most of the hard work is in the first half of the semester
Load balanced with most other classes
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Luke Huan Univ. of Kansas

26. Luke Huan Univ. of Kansas
Why take this class?
E. Looks good on my resume.
Yes, but why? This is not a course for:
Oracle administrators
IBM DB2 engine developers
Though it’s useful for both!
It is a course for well-educated computer scientists
Database system concepts and techniques increasingly used “outside the box”
Ask your friends at Microsoft, Yahoo!, Google, Apple, etc.
Actually, they may or may not realize it!
A rich understanding of these issues is a basic and (un?)fortunately unusual skill.
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Luke Huan Univ. of Kansas

27. Luke Huan Univ. of Kansas
Who?
Instructors
Prof. Luke Huan, EECS
Prof. Office Hours:
Eaton Hall 2034, M, W 4:15-5:15pm
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Luke Huan Univ. of Kansas

28. Luke Huan Univ. of Kansas
How? Workload
Projects with a “real world” focus:
Build a web-based application w/PostgreSQL and your favorite internet programming languge (PHP, JAVA, PERL, just naming a few)
Homework assignments and quizzes
Exams – 1 Midterm & 1 Final
Projects to be done in groups of 2
Pick your partner ASAP
The course is “front-loaded”
most of the hard work is in the first half
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Luke Huan Univ. of Kansas

29. Luke Huan Univ. of Kansas
How? Administrative
Text book: Elmasri & Navatgh 5th edition
Class website - people.eecs.ku.edu/~jhuan/EECS647
read it regularly
Please include eecs 647 in your mail to the instructor (for quick response)
Grading, hand-in policies, etc. is on syllabus
* The textbook will be available at the KU bookstore today or tomorrow
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Luke Huan Univ. of Kansas

30. Luke Huan Univ. of Kansas
Academic Misconduct
We take academic misconduct very seriously.
We encourage student to work together for doing homework and projects, but each student should write down their own solution.
You are absolutely encouraged to discuss with your classmates about your homework assignments, programming exercises, and final projects
You are responsible for all your works
For homework assignments and projects resulted from discussion, please always acknowledge other people’s contribution by including a sentence at the beginning of the hand-in saying “I discussed the homework (project) with XXX (include more names if necessary)”. There is absolutely NO penalty for doing so.
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Luke Huan Univ. of Kansas

31. Agenda for the rest of today
Today: a preview of the class contents:
ER model
Logical database design
File system
Transaction
Data mining
Database in the future
This Wednesday
the Entity-Relationship model
Today’s lecture is from Chapter 1 and 2 in E & N
Read Chapter 3 for next class.
Relational model
SQL
Query processing
XML
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Luke Huan Univ. of Kansas

32. Luke Huan Univ. of Kansas
Agenda …
Design a Database
ER model
Relational model
Database logical design
Query with SQL
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Luke Huan Univ. of Kansas

33. Data Models Describe Data
A data model is a collection of concepts for describing data.
Different levels of data models
Conceptual (semantic) data model uses data (facts) to describe a physical world
Representational model describes data in database management systems
Physical data model describe how data is stored in files in computers.
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34. An ER Model for a mini-World
Salary
name
Employees
ssn
name
manager
number
Departments
Works_For
Entity: Real-world object distinguishable from other objects. An entity is described (in DB) using a set of attributes.
Relationship: Association among two or more entities. E.g., John works in Pharmacy department. 4

35. Relational Model Describes Data
Relational model is the most popular representational data model that are used by current commercial DBMS.
Relational model describes data using tables
SSN
Name
Salary
John Smith
30000
Franklin Wong
40000
Joyce English
25000
Salary
name
Employees
ssn
Cardinality = 3, degree = 3, all rows distinct
Do all columns in a relation instance have to be distinct?
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36. Logical Database Design
Salary
name
Employees
ssn
name
manager
number
Departments
Works_For
SSN
Name
Salary
John Smith
30000
Franklin Wong
40000
Joyce English
25000
DNumber
DName
Manager 5
research
SSN
Dnum 5
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Luke Huan Univ. of Kansas

37. Logical Database Design (Cont.)
Salary
name
Employees
ssn
name
manager
number
Departments
Works_For
SSN
Name
Salary
DNum
John Smith
30000 5
Franklin Wong
40000
Joyce English
25000
DNumber
DName
Manager 5
research
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Luke Huan Univ. of Kansas

38. Logical Database Design (Cont.)
Salary
name
Employees
ssn
name
manager
number
Departments
Works_For
SSN
Name
Salary
DNumber
DName
Manager
John Smith
30000 5
research
Franklin Wong
40000
Joyce English
25000
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Luke Huan Univ. of Kansas

39. SQL: Query Information from a Database
Query 1: Retrieve the salary of Franklin Wong
Q1: SELECT SALARY FROM EMPLOYEE WHERE NAME=‘Franklin Wong‘
Answer: 40000
SSN
Name
Salary
John Smith
30000
Franklin Wong
40000
Joyce English
25000
12/31/2018
Luke Huan Univ. of Kansas

40. Luke Huan Univ. of Kansas
Agenda …
Design a Database Management System
File systems
Disk storage
Indexing
Query processing
Transactions
Concurrency
Recovery
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Luke Huan Univ. of Kansas

41. Components of a Disk The platters spin (say, 90rps).
Spindle
Tracks
Disk head
The platters spin (say, 90rps).
The arm assembly is moved in or out to position a head on a desired track. Tracks under heads make a cylinder (imaginary!).
Sector
Arm movement
Platters
Arm assembly 21

42. Indexing is the Key to Speed up Disk Operations
``Find all employees whose salary > $25000’’
If data is in sorted file, do binary search to find first such employee, then scan to find others.
Cost of binary search can be quite high.
Simple idea: Create an `index’ file.
Index File k1 k2 kN
Data File
Page 1
Page 2
Page 3
Page N
Can do binary search on (smaller) index file! 3

43. Concurrent execution of user programs
Why?
Utilize CPU while waiting for disk I/O
(database programs make heavy use of disk)
Avoid short programs waiting behind long ones
e.g. ATM withdrawal while bank manager sums balance across all accounts
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Luke Huan Univ. of Kansas

44. Key concept: Transaction
an atomic sequence of database actions (reads/writes)
takes DB from one consistent state to another
transaction
consistent state 1
consistent state 2
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Luke Huan Univ. of Kansas

45. Luke Huan Univ. of Kansas
Example
Transaction
“transfer $100 from Saving to checking”
checking: $300
savings: $900
checking: $200
savings: $1000
Here, consistency is based on our knowledge of banking “semantics”
In general, up to writer of transaction to ensure transaction preserves consistency
DBMS provides (limited) automatic enforcement, via integrity constraints
e.g., balances must be >= 0
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Luke Huan Univ. of Kansas

46. Luke Huan Univ. of Kansas
Agenda …
Advanced topics
XML
Data mining
Association
Classification
Clustering
Database in the future
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Luke Huan Univ. of Kansas