Lecture 1 (1) (2).pdf

Lecture 1 Introduction to DBMS. Data Modeling. Senior Lecturer: Tulebayev Yersultan  Introduction to DBMS. Data Modeling: PART I. What is a database? Properties, Characteristics, Database Management System, Application, Example. PART II. Types of database models. Advantages and...

Lecture 1 Introduction to DBMS. Data Modeling. Senior Lecturer: Tulebayev Yersultan  Introduction to DBMS. Data Modeling: PART I. What is a database? Properties, Characteristics, Database Management System, Application, Example. PART II. Types of database models. Advantages and disadvantages. PART III. ER Diagram. Entity, Attributes, Relationships. PART I. What is a database? Properties, Characteristics, Database Management System, Application, Example.  What is a database? A database is a collection of information that is organized so that it can easily be accessed, managed, and updated. Properties of a database: A database represents some aspect of the real world, sometimes called the miniworld or the universe of discourse (UoD). Changes to the miniworld are reflected in the database. A database is a logically coherent collection of data with some inherent meaning. A random assortment of data cannot correctly be referred to as a database. A database is designed, built, and populated with data for a specific purpose. It has an intended group of users and some preconceived applications in which these users are interested.  Potential problems: Size of data Ease of updating Accuracy of data Security of data Redundancy of data Importance of data What is a database management system? A database management system (DBMS) is system software for creating and managing databases. A DBMS makes it possible for end users to create, protect, read, update and delete data in a database. Example of a DBMS - The STUDENT file stores data of each student - The COURSE file stores contain data on each course - The SECTION stores the information about sections in a particular course - The GRADE_REPORT file stores the grades which students receive in the various sections - The PREREQUISITE file contains information about pre- courses Characteristics of Database Management System: - Provides security and removes redundancy - Self-describing nature of a database system - Insulation between programs and data abstraction - Support of multiple views of the data - Sharing of data and multiuser transaction processing - DBMS allows entities and relations among them to form tables. - It follows the ACID concept ( Atomicity, Consistency, Isolation, and Durability). - DBMS supports multi-user environment that allows users to access and manipulate data in parallel. Three-Schema Architecture: Users in a DBMS environment Application of DBMS: PART II. Types of database models. Advantages and disadvantages. Types of database models: 1. Hierarchical Database 2. Network Database 3. Relational Database 4. Object-Oriented Model Type 1. Hierarchical Database A hierarchical database is a data model in which data is stored in the form of records and organized into a tree-like structure, or parent-child structure, in which one parent node can have many child nodes connected through links. Example of hierarchical database Advantages of the Hierarchical DBMS : Data can be retrieved easily due to the explicit links present between the table structures. Referential integrity is always maintained i.e. any changes made in the parent table are automatically updated in a child table. Promotes data sharing. It is conceptually simple due to the parent-child relationship. Database security is enforced. Efficient with 1: N relationships. A clear chain of command or authority. Increases specialization. High performance. Clear results. Disadvantages of the Hierarchical DBMS : If the parent table and child table are unrelated then adding a new entry in the child table is difficult because additional entry must be added in the parent table. Complex relationships are not supported. Redundancy which results in inaccurate information. Change in structure leads to change in all application programs. M: N relationship is not supported. No data manipulation or data definition language. Lack of standards. Poor flexibility Organizational Disunity and Rigid structure. Type 2. Network database The network database model was a progression from the hierarchical database model and was designed to solve some of that model's problems, specifically the lack of flexibility. Instead of only allowing each child to have one parent, this model allows each child to have multiple parents Example of Network DBMS: Advantages of the Network DBMS: fast data access. It also allows users to create queries that are more complex than those they created using a hierarchical database. So, a variety of queries can be run over this model. Disadvantages of the Network DBMS: A user must be very familiar with the structure of the database to work through the set structures. Updating inside this database is a tedious task. One cannot change a set structure without affecting the application programs that use this structure to navigate through the data. If you change a set structure, you must also modify all references made from within the application program to that structure. Type 3. Relational Database A relational model organizes data into one or more tables (or "relations") of columns and rows, with a unique key identifying each row. Rows are also called records or tuples. Columns are also called attributes. Example of the Relational DBMS: Advantages of using RDBMS: Ease of Use Network Access Language Performance Prevents Data Redundancy Privileges and Data Security Disadvantages of RDBMS: Cost Lack of Speed Memory Space  POPULAR RELATIONAL DATABASE MANAGEMENT SYSTEMS: Oracle SQL Server MySQL PostgreSQL SQLite Type 4. Object-Oriented Model An object-oriented database (OOD) is a database system that can work with complex data objects — that is, objects that mirror those used in object-oriented programming languages. In object- oriented programming (OOP), everything is an object.  Elements of Object-Oriented data model: Object Attributes and Method Class Inheritance Example of Object-Oriented data model: Advantages of Object-Oriented data model: Reusability: generic objects can be defined and then reused in numerous application. Complex data types: Can manage complex data such as document, graphics, images, voice messages, etc. Distributed databases: Due to mode of communication between objects, OODBMS can support distribution of data across networks more easily. Disadvantages of Object Oriented Databases: - Competition - Complexity - Lack of support for views - Lack of support for security - Lack of standards - Lack of experience - Lack of universal data model - Query Optimization compromises encapsulation PART III. ER Diagram. Entity, Attributes, Relationships. ENTITY RELATIONAL (ER) MODEL is a high-level conceptual data model diagram. ER modeling helps you to analyze data requirements systematically to produce a well-designed database. The Entity-Relation model represents real-world entities and the relationship between them. ER DIAGRAMS ENTITY-RELATIONSHIP DIAGRAM (ERD) displays the relationships of entity set stored in a database. In other words, we can say that ER diagrams help you to explain the logical structure of databases. Why use ER Diagrams? Helps you to define terms related to entity relationship modeling Provide a preview of how all your tables should connect, what fields are Helps to describe entities, attributes, relationships ER diagrams are translatable into relational tables which allows you to build databases quickly ER diagrams can be used by database designers as a blueprint for implementing data in specific software applications The database designer gains a better understanding of the information to be contained in the database with the help of ERP diagram ERD is allowed you to communicate with the logical structure of the database to users Components of the ER Diagram Entities Attributes Relationships WHAT IS ENTITY? A real-world thing either living or non-living that is easily recognizable and nonrecognizable. An entity can be place, person, object, event or a concept, which stores data in the database. Examples of entities: Person: Employee, Student, Patient Place: Store, Building Object: Machine, product, and Car Event: Sale, Registration, Renewal Concept: Account, Course ATTRIBUTES Entities are represented by their properties, which also called attributes. For example, a student entity may have a name, age, class, as attributes. Relationships There are three types of relationships between entities (tables) in data modeling: One-to-many relationships (also denoted as 1:M). Many-to-many relationships (M:N). One-to-one relationships (1:1). Let's study them with an example: