1. 1 CENG 302 Introduction to Database Management Systems Nihan Kesim Çiçekli email: nihan@ceng.metu.edu.tr URL: http://www.ceng.metu.edu.tr/~nihan/ceng302

2. 2 CENG 302 Instructor: Nihan Kesim Çiçekli Office: A308 Email: nihan@ceng.metu.edu.tr Lecture Hours: Tue. 10:40-11:30 (IE102); Thu. 13:40-15:30 (IE102) Course Web page: http://www.ceng.metu.edu.tr/~nihan/ceng302 Teaching Assistant: Ali Anıl Sınacı

3. 3 Text Books and References 1.Raghu Ramakrishnan, Database Management Systems, McGraw Hill, 3 rd edition, 2003 (text book). 2.R. Elmasri, S.B. Navathe, Fundamentals of Database Systems, 4 th edition, Addison-Wesley, 2004. 3.A. Silberschatz, H.F. Korth, S. Sudarshan, Database System Concepts, McGraw Hill, 4 th edition, 2002.

4. 4 Grading Assignments 20 % Midterm 125 % Midterm 2 25 % Final Exam30 %

5. 5 Grading Policies Policy on missed midterm: –no make-up exam Lateness policy: –Late assignments are penalized up to 10% per day. All assignments are to be your own work.

6. 6 Course Outline Introduction to Relational Database Management Systems The Relational Data Model Relational Algebra SQL QBE Entity-Relationship Model Relational Database Design: Normalization Secondary Storage Devices Sequential Files Indexed Sequential Files Hashing

7. 7 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 CENG302)  A Database Management System (DBMS) is a software package designed to store and manage databases.

8. 8 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 ?

9. 9 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.

10. 10 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.

11. 11 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)

12. 12 Instance of Students Relation Students( sid: string, name: string, login: string, age: integer, gpa: real ) sidnameloginagegpa 53666Jonesjones@cs183.4jones@cs 53688Smithsmith@ee183.2smith@ee 53650Smithsmith@math193.8smith@math

13. 13 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.  Schemas are defined using DDL; data is modified/queried using DML. Physical Schema Conceptual Schema External Schema 1 External Schema 3 External Schema 2

14. 14 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!

15. 15 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 These layers must consider concurrency control and recovery