Introduction to Database Systems

This lecture introduces database concepts and database management systems.
The course covers introductions to databases and DBMS, their characteristics, database models, ER models, relational DB schemas, database normalization, relational algebra, database concurrency, and lock conversion.
"Fundamentals of Database Systems" SIXTH EDITION by Ramez Elmasri and Shamkant B. Navathe is used as a reference.

Databases are used in banks, hotels, libraries, and supermarkets.
Traditional database applications predominantly store and access textual or numeric information.
Technology advances have led to new database applications
Multimedia databases store images, audio, and video digitally.
Geographic Information Systems (GIS) can store and analyze maps, weather data, and satellite images.
Real-time and active database technology controls industrial and manufacturing processes.
Data warehouses and online analytical processing (OLAP) extract and analyze business information from large databases to support decision-making.
Database search techniques are used on the WWW to improve information retrieval for Internet users.

A database is a collection of related data which includes known facts that can be recorded and have implicit meaning.
Names, telephone numbers, and addresses are examples of data.
Data can be recorded in an address book or stored on a hard drive using software like Microsoft Access or Excel.

A database represents a miniworld or a universe of discourse (UoD), and changes to this miniworld are reflected in the database.
A database is a logically coherent collection of data with inherent meaning, not a random assortment.
Databases are designed, built, and populated for specific purposes with intended users and applications.
A database can vary in size and complexity.

A database management system (DBMS) is a collection of programs that allows users to create and maintain a database.
DBMS is a general-purpose software that helps in defining, constructing, manipulating, and sharing databases among users and applications.

Defining a database involves specifying data types, structures, and constraints.
Database definitions are stored by the DBMS in a database catalog or dictionary, known as meta-data.
Constructing a database involves storing data on a storage medium controlled by the DBMS.
Manipulating a database includes querying to retrieve data, updating to reflect changes, and generating reports.
Sharing a database allows simultaneous access by multiple users and programs.

Application programs access databases by sending queries or requests to the DBMS.
Queries retrieve data, and transactions may read and write data.

Important functions include protecting and maintaining the database over time.
Protection includes system protection against malfunctions and security protection against unauthorized access.
Maintaining involves adapting the database system to evolving requirements.

A university database maintains information about students, courses, and grades.
Defining the database requires specifying the structure of records and data element types.
A COURSE record includes Course_name, Course_number, Credit_hours, and Department.
Data types must be specified for each element, like strings for names or integers for student numbers.
Coding schemes can represent data item values, like class standing (1 for freshman, 2 for sophomore, etc.).

Constructing the database involves storing data for students, courses, sections, grades, and prerequisites in appropriate files.
Records in different files may be related.
Database manipulation involves querying and updating.
Examples of queries include retrieving a list of courses and grades for a student.
Updates include changing a student's class or entering grades.