1. Introduction to Database Systems
Ref. Ramakrishnan & Gehrke Chapter 1
The slides for this text are organized into chapters. This lecture covers Chapter 1.
Chapter 1: Introduction to Database Systems
Chapter 2: The Entity-Relationship Model
Chapter 3: The Relational Model
Chapter 4 (Part A): Relational Algebra
Chapter 4 (Part B): Relational Calculus
Chapter 5: SQL: Queries, Programming, Triggers
Chapter 6: Query-by-Example (QBE)
Chapter 7: Storing Data: Disks and Files
Chapter 8: File Organizations and Indexing
Chapter 9: Tree-Structured Indexing
Chapter 10: Hash-Based Indexing
Chapter 11: External Sorting
Chapter 12 (Part A): Evaluation of Relational Operators
Chapter 12 (Part B): Evaluation of Relational Operators: Other Techniques
Chapter 13: Introduction to Query Optimization
Chapter 14: A Typical Relational Optimizer
Chapter 15: Schema Refinement and Normal Forms
Chapter 16 (Part A): Physical Database Design
Chapter 16 (Part B): Database Tuning
Chapter 17: Security
Chapter 18: Transaction Management Overview
Chapter 19: Concurrency Control
Chapter 20: Crash Recovery
Chapter 21: Parallel and Distributed Databases
Chapter 22: Internet Databases
Chapter 23: Decision Support
Chapter 24: Data Mining
Chapter 25: Object-Database Systems
Chapter 26: Spatial Data Management
Chapter 27: Deductive Databases
Chapter 28: Additional Topics

2. What Is a DBMS? A very large, integrated collection of data.
Models real-world enterprise.
Entities (e.g., students, courses)
Relationships (e.g., Tarkan is taking CENG351)
A Database Management System (DBMS) is a software package designed to store and manage databases.

3. Why Study Databases?? ? Shift from computation to information
at the “low end”: scramble to webspace (a mess!)
at the “high end”: scientific applications
Datasets increasing in diversity and volume.
Digital libraries, interactive video, Human Genome project, EOS project
... need for DBMS exploding
DBMS encompasses most of CS
OS, languages, theory, “AI”, multimedia, logic

4. Why Use a DBMS? Data independence and efficient access.
Reduced application development time.
Data integrity and security.
Uniform data administration.
Concurrent access, recovery from crashes. 3

5. Data Models
A data model is a collection of concepts for describing data.
A schema is a description of a particular collection of data, using the given data model.
The relational model of data is the most widely used model today.
Main concept: relation, basically a table with rows and columns.
Every relation has a schema, which describes the columns, or fields. 5

6. Example: University Database
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)
Physical schema:
Relations stored as unordered files.
Index on first column of Students.
External Schema (View):
Course_info(cid:string,enrollment:integer) 7

7. Instance of Students Relation
Students( sid: string, name: string, login: string,
age: integer, gpa: real )
sid name login age gpa
53666 Jones
53688 Smith
53650 Smith

8. Levels of Abstraction
Many external schemata, single conceptual(logical) schema and physical schema.
External schemata describe how users see the data.
Conceptual schema defines logical structure
Physical schema describes the files and indexes used.
External
Schema 1
External
Schema 2
External
Schema 3
Conceptual Schema
Physical Schema
Schemas are defined using DDL; data is modified/queried using DML. 6

9. Data Independence
Applications insulated from how data is structured and stored.
Logical data independence: Protection from changes in logical structure of data.
Physical data independence: Protection from changes in physical structure of data.
One of the most important benefits of using a DBMS!

10. Files and Access Methods
These layers
must consider
concurrency
control and
recovery
Structure of a DBMS
A typical DBMS has a layered architecture.
This is one of several possible architectures; each system has its own variations.
Query Optimization
and Execution
Relational Operators
Files and Access Methods
Buffer Management
Disk Space Management DB 22