Introduction to Databases and DBMS

• This lecture introduces database concepts and database management systems (DBMS).

Course Topics

• Introduction to DB and DBMS
• Characteristics of DB and Database Users
• Database Models
• Entity Relation[ER] Model
• Relational DB Schema
• Database Normalization
• The Relational Algebra
• Databases Concurrency
• Lock Conversion

Where Databases are Used

• Banks
• Hotels
• Libraries
• Supermarkets

Traditional Database Applications

• Applications where most of the information is textual or numeric

New Applications of DB Systems

• Multimedia Databases: stores images, audio and video digitally
• Geographic Information Systems (GIS): stores and analyzes maps, weather data and satellite images
• Real-time and active database technology: controls industrial and manufacturing processes
• Data warehouses and online analytical processing (OLAP): extracts and analyzes business information from large databases
• Database search techniques are applied to the WWW: to improve information search on the internet

Databases Defined

• A database represents some aspect of the real world referred to as the miniworld or the universe of discourse (UoD).
• A database is a collection of related data.
• Data represents known facts that can be recorded and have implicit meaning.
• A database is a logically coherent collection of data with inherent meaning.
• Changes to the miniworld are reflected in the database.
• Designed, built, and populated for a specific purpose and for an intended group of users.
• It can be of any size and complexity.

DBMS Defined

• A database management system (DBMS) is a collection of programs allowing users to create and maintain a database.
• DBMS is a general-purpose software system that facilitates defining, constructing, manipulating, and sharing databases among various users and applications.
• Defining a database specifies data types, structures, and constraints.
• The database definition is stored by the DBMS in a database catalog or dictionary, known as meta-data.
• Constructing the database involves storing data on a storage medium controlled by the DBMS.
• Manipulating a database: includes querying data, updating to reflect changes, and generating reports.
• Sharing a database: allows multiple users and programs to access the database simultaneously.
• An application program: accesses the database by sending queries or requests to the DBMS.
• A query: retrieves data.
• A transaction: may read and write data into the database.

DBMS Functions

• DBMS protects the database and maintains it over time.
• System Protection: protects against hardware or software malfunction.
• Security Protection: protects against unauthorized or malicious access.
• Maintaining a database: allows for evolving to meet changing requirements over a long life cycle.
• Special-purpose DBMS software can be created to manage a database.
• Most DBMS are complex software systems.

University Database Example

• A UNIVERSITY database maintains information about students, courses, and grades.
• Defining this database: requires specifying the structure of records and data elements within each record.
• Data types must be specified for each data element.
• The STUDENT Name is a string, Student_number is an integer, the GRADE_REPORT is a single character from the set {‘A’, ‘B’, ‘C’, ‘D’, ‘F’, ‘I’}.
• Constructing the database: involves storing data for each student, course, section, grade report, and prerequisites.
• Database manipulation: includes querying and updating the database.
• Examples of queries: retrieving lists of courses and grades for a student.
• Example updates: changing student details, creating a new course section or entering grades.