1. Database Management System
Introduction

2. Warning
This class is a lot of work.
But it is worth it.
Of all courses you take at CS, this may be the one that gets you a job.

3. Syllabus The background and history of database management systems.
The fundamentals of using a database management systems.
Relational model.
Queries and Updates.
Relational Algebra.
Normalization
Transactions and Security.
Object-oriented, object-relational, semi-structured and XML database systems.

4. What Is a Database System?
Database: a very large, integrated collection of data.
Models a real-world enterprise
Entities (e.g., teams, games)
Relationships (e.g., Abo Teraka is playing in Al Ahly)
More recently, also includes active components , often called “business logic”. (e.g., the BCS ranking system)
A Database Management System (DBMS) is a software system designed to store, manage, and facilitate access to databases.

5. Why Study Databases?? ? Shift from computation to information
always true for corporate computing
Web made this point for personal computing
more and more true for scientific computing
Need for DBMS has exploded in the last years
Corporate: retail swipe/clickstreams, “customer relationship”, “supply chain”, “data warehouses”, etc.
Scientific: digital libraries, Human Genome project, NASA Mission to Planet Earth, physical sensors, grid physics network
DBMS encompasses much of CS in a practical discipline
OS, languages, theory, AI, multimedia, logic
Yet traditional focus on real-world apps

6. databases you may use

7. Database Applications
These examples are what we called traditional database applications
(First part of book focuses on traditional applications)
More Recent Applications:
Youtube
iTunes
Geographic Information Systems (GIS)
Data Warehouses
Many other applications

8. Database Systems: Then

9. History of Database Systems
1950’s and early 1960’s:
Data processing using magnetic tapes for storage
Tapes provide only sequential access
Punched cards for input
Late 1960’s and 1970’s:
Hard disks allow direct access to data
Network and hierarchical data models in widespread use
Ted Codd defines the relational data model
Would win the ACM Turing Award for this work
IBM Research begins System R prototype
UC Berkeley begins Ingres prototype
High-performance (for the era) transaction processing

10. History (cont.)
1980s:
Research relational prototypes evolve into commercial systems
SQL becomes industry standard
Parallel and distributed database systems
Object-oriented database systems
1990s:
Large decision support and data-mining applications
Large multi-terabyte data warehouses
Emergence of Web commerce
2000s:
XML and XQuery standards
Automated database administration
Increasing use of highly parallel database systems
Web-scale distributed data storage systems

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

12. Can we do it without a DBMS ?
Sure we can! Start by storing the data in files:
students.txt courses.txt professors.txt
Now write C or Java programs to implement specific tasks

13. Doing it without a DBMS... Read ‘students.txt’ Read ‘courses.txt’
Write a C program to do the following:
Enroll “Mary Johnson” in “CSE444”:
Read ‘students.txt’
Read ‘courses.txt’
Find&update the record “Ahmed Hassan”
Find&update the record “CS444”
Write “students.txt”
Write “courses.txt”

14. Database server (someone else’s C program)
Enters a DMBS
“Two tier database system”
Database server (someone else’s C program)
Applications
Data files

15. Problems without a DBMS...
System crashes:
What is the problem ?
Large data sets (say 50GB)
Simultaneous access by many users
Need locks: we know them from OS, but now data on disk; and is there any fun to re-implement them ?
Read ‘students.txt’
Read ‘courses.txt’
Find&update the record “Mary Johnson”
Find&update the record “CSE444”
Write “students.txt”
Write “courses.txt”
CRASH !

16. Why Use a DBMS? There is no control or coordination of what
Access by a collection
of ad hoc programs
in C++, Java, PHP, etc.
Without a DBMS, we'd have:
users of
the data
There is no control or
coordination of what
these programs do with the data
data stored as bits on disks
organized as files

17. Why Use a DBMS?
applications
With a DBMS, we have:
DBMS
users of
the data
data stored as bits on disks
organized as files
DBMS provides control and coordination to protect the data.

18. Database definition
Database is “data” or facts supplied by a base or software
Files contain data with the same structure
Database is an integration of different kinds of data

19. Database Systems The big commercial database vendors:
Oracle
IBM (with DB2) bought Informix recently
Microsoft (SQL Server)
Sybase
Some free database systems (Unix) :
Postgres
Mysql
Predator

20. DBMS Functions Define the database Construct the database
Manipulating database
Data security and integrity
Concurrency
Recovery

21. Disadvantages of database
Expensive
Incompatible with any other DBMS

22. Concurrency A DBMS supports access by concurrent users
concurrent = happening at the same time
concurrent access, particularly writes (data changes), can result in inconsistent states (even when the individual operations are correct)
the DBMS can check the actual operations of concurrent users, to prevent activity that will lead to inconsistent states

23. Access Control A DBMS can restrict access to authorized users
security policies often require control that is more fine-grained than that provided by a file system
since the DBMS understands the data structure, it can enforce fairly sophisticated and detailed security policies
on subsets of the data
on subsets of the available operations

24. Redundancy Control A DBMS can assist in controlling redundancy
redundancy = multiple copies of the same data
with file storage, it's often convenient to store multiple copies of the same data, so that it's "local" to other data and applications
this can cause many problems:
wasted disk space
inconsistencies
need to enter the data multiple times

25. Backup and Recovery A DBMS can provide backup and recovery
backup = snapshots of the data particular times
recovery = restoring the data to a consistent state after a system crash
the higher level semantics (relationships and constraints) can make it difficult to restore a consistent state
transaction analysis can allow a DBMS to reconstruct a consistent state from a number of backups

26. Views and Interfaces
A DBMS can support multiple user interfaces and user views
since the DBMS provides a well-defined data model and a persistent data dictionary, many different interfaces can be developed to access the same data
data independence ensures that these UIs will not be made invalid by most changes to the data
new user views can be supported as new schemas defined against the conceptual schema

27. Database Components Application Programs DBMS Design tools Database
===============
Design tools
Table Creation
Form Creation
Query Creation
Report Creation
Procedural
language
compiler (4GL)
=============
Run time
Form processor
Query processor
Report Writer
Language Run time
User
Interface
Applications
Application
Programs
Database
Database contains:
User’s Data
Metadata
Indexes
Application Metadata

28. Actors on DBMS Database Administrator System analysis
Database designer
Application programmer
End user

29. Actors on the Scene Database Administrators acquiring a DBMS
managing the system
acquiring HW and SW to support the DBMS
authorizing access (security policies)
managing staff, including DB designers

30. Actors on the Scene Database Designers
identifying the information of interested in the Universe of Discourse (UoD)
designing the database conceptual schema
designing views for particular users
designing the physical data layout and logical schema
adjusting data parameters for performance

31. Actors on the Scene
Systems Analysts and Application Programmers (generic database developers)
provide specialized knowledge to optimize database usage
provide generic (canned) application programs

32. Actors on the Scene End Users casual users: ad-hoc queries
naïve or parametric users: canned queries such as menus for a phone company customer service agent
sophisticated users: people who understand the system and the data and use it in many novel ways
standalone users: people who use personal easy-to-use databases for personal data

33. Three-Schema Architecture
user-specific
views
External View
External View
External View
Conceptual Schema
generic view
Internal Schema
physical view

34. Levels of Abstraction Users DB Views describe how users see the data.
Conceptual schema defines logical structure
Physical schema describes the files and indexes used.
(sometimes called the ANSI/SPARC model)
Physical Schema
Conceptual Schema
View 1
View 2
View 3 DB 6

35. Example: University Database
Physical Schema
Conceptual Schema
View 1
View 2
View 3 DB
Conceptual schema:
Students(sid: string, name: string, login: string,
age: integer, gpa:real)
Courses(cid: string, cname:string, credits:integer)
Enrolled(sid:string, cid:string, grade:string)
External Schema (View):
Course_info(cid:string,enrollment:integer)
Physical schema:
Relations stored as unordered files.
Index on first column of Students. 7

36. Levels of Abstraction
Physical level: describes how a record (e.g., customer) is stored.
Logical level: describes data stored in database, and the relationships among the data.
type customer = record
customer_id : string; customer_name : string; customer_street : string; customer_city : string;
end;
View level: application programs hide details of data types. Views can also hide information (such as an employee’s salary) for security purposes.

37. Conceptual Data Models
A data model describes the possible schemas (essentially the meta-schema)
A DBMS is designed around a particular data model
this is what allows all system components (and humans) to understand the schema and data
possible data models
relational, object-oriented, object-relational, entity-relationship, semantic, network, hierarchical, etc.

38. Physical Data Models
A physical data model describes the way in which data is stored in the computer
typically only of interest to database designers, implementers and maintainers …not end users
must provide a well-defined structure that can be mapped to the conceptual schema
allows optimization strategies to be defined generically

39. Instances and Schemas
Similar to types and variables in programming languages
Schema – the logical structure of the database
Example: The database consists of information about a set of customers and accounts and the relationship between them)
Physical schema: database design at the physical level
Logical schema: database design at the logical level
Instance – the actual content of the database at a particular point in time

40. Classification DBMS has 3 criteria as
Data models (relational & object &….)
Number of users (single user & Multi-user)
Number of sites (Centralized & Distributed)

41. Data model
Is a technique for organization data and concepts to describe the structure of data, relationship and integrity constrains.

42. Database models Relational data model
Oracle, Access
Hierarchical data mode (as a tree)
IMS DBMS
Network data model (as a graph)
IDMS DBMS
Object oriented model
VERSANT DBMS
Object relational data model
UNISQL DBMS

43. Data Models Hierarchical Model (1960’s and 1970’s)
Similar to data structures in programming languages.
Books
(id, title)
Publisher
Subjects
Authors
(first, last)

44. Data Models Network Model (1970’s)
Provides for single entries of data and navigational “links” through chains of data.
Subjects
Books
Authors
Publishers

45. Data Models Object Oriented Data Model (1990’s)
Encapsulates data and operations as “Objects”
Books
(id, title)
Publisher
Subjects
Authors
(first, last)

46. Relational Model Example of tabular data in the relational model
Attributes

47. A Sample Relational Database

48. Relational data model Based on the relations between data
Each relation or table (entity) is a data structure or a collection of attributes describing data
Attribute or a field is a column in the table
A tuple or record is a raw in the table

49. Relational data model
Null value is assigned to attribute which means that the attribute is not yet known
Primary key is a unique identifier for the table. One attribute or combination of attributes

50. Relational data model
Foreign key is an attribute (combination of attributes) is one relation whose values are required to match those of the primary of some relation
Candidate key is any key (primary or foreign keys)

51. New Trends in Databases
Object-relational databases
Main memory database systems
XML XML XML !
Relational databases with XML support
Middleware between XML and relational databases
Native XML database systems
Lots of research here at UW on XML and databases
Data integration
Peer to peer, stream data management – still research

52. SQL SQL: widely used non-procedural language
Example: Find the name of the customer with customer-id select customer.customer_name from customer where customer.customer_id = ‘ ’
Example: Find the balances of all accounts held by the customer with customer-id select account.balance from depositor, account where depositor.customer_id = ‘ ’ and depositor.account_number = account.account_number
Application programs generally access databases through one of
Language extensions to allow embedded SQL
Application program interface (e.g., ODBC/JDBC) which allow SQL queries to be sent to a database

53. The Entity-Relationship Model
Models an enterprise as a collection of entities and relationships
Entity: a “thing” or “object” in the enterprise that is distinguishable from other objects
Described by a set of attributes
Relationship: an association among several entities
Represented diagrammatically by an entity-relationship diagram:

54. Transaction Management
A transaction is a collection of operations that performs a single logical function in a database application
Transaction-management component ensures that the database remains in a consistent (correct) state despite system failures (e.g., power failures and operating system crashes) and transaction failures.
Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database.

55. An UNIVERSITY example
A UNIVERSITY database for maintaining information concerning students, courses, and grades in a university environment
We have:
STUDENT file stores data on each student
COURSE file stores data on each course
SECTION file stores data on each section of each course
GRADE_REPORT file stores the grades that students receive
PREREQUISITE file stores the prerequisites

56. Example of a simple database

57. COMPANY Database
The company is organized into DEPARTMENTs. Each department has a name, number, and an employee who manages the department. We keep track of the start date of the department manager. A department may have several locations.
Each department controls a number of PROJECTs. Each project has a name, number, and is located at a single location.

58. COMPANY Database
We store each EMPLOYEE's social security number, address, salary, sex, and birth date. Each employee works for one department but may work on several projects. We keep track of the number of hours per week that an employee currently works on each project. We also keep track of the direct supervisor of each employee.
Each employee may have a number of DEPENDENTs. For each dependent, we keep their name, sex, birth date, and relationship to the employee.