DBMS Lecture1.ppt
- 1. Data Base Management System(CS503) Lecture 1 Prepared by: Mrs. Ipsita Saha Assistant Professor Department of CSE Guru Nanak Institute of Technology Kolkata, India 1
- 2. Definitions Purpose of Database DBMS vs. File Management System Data Model Text Books: 1. Henry F. Korth and Silberschatz Abraham, “Database System Concepts”, Mc.Graw Hill. 2. Elmasri Ramez and Novathe Shamkant, “Fundamentals of Database Systems”, Benjamin Cummings Publishing. Company. Reference: 1. Jain: Advanced Database Management System CyberTech 2. Date C. J., “Introduction to Database Management”, Vol. I, II, III, Addison Wesley. 3. “Fundamentals of Database Systems”, Ramez Elmasri, Shamkant B.Navathe, Addison Wesley Publishing Edition 2 Books: Contents:
- 3. Definitions: Data: Collection of facts & figures. DATABASE : A well organized collection of data following a particular architecture and the architecture should support an efficient data storage and retrieval mechanism. e.g. Record of students stored in files, Information stored over internet DATABASE MANAGEMENT SYSTEM: DBMS is a software for creating and managing databases that provides a systematic way to create, retrieve, update and manage data. e.g. MySQL Microsoft Access FileMaker FoxPro 3
- 4. Purpose of database : 1. It reduces Data Redundancy to a large extent. 2. It controls Data Inconsistency. 3. It facilitates Sharing of data. 4. It ensures Data Security. 5. It allows query processing to access data. 4 Name DOB Admission Status Smith 10-Jun-1992 Admitted John 15-Jan-1991 Not Admitted Ankush 12-Mar-1993 Admitted John 15-Jan-1991 Not Admitted Name DOB Admission Status Smith 10-Jun-1992 Not Admitted John 15-Jan-1991 Not Admitted Ankush 12-Mar-1993 Admitted Smith 10-Jun-1992 Admitted Data Redundancy Data Inconsistency
- 5. What is File Management System? • A file management system handles how to read and write data to the hard disk. When installing the operating system, the file system also installs to the computer. • For examples, OS such as Linux and Windows provide files systems. It stores data to the hard disk and storing and retrieving data occurs through this file management system. • In a file system, each user implements files according to the requirement. • For example, in a sales department, one employee might store the details of sales personnel’s, and another employee might store details of the salaries. The same data might be replicated. So, there can be a data redundancy. When updating data, the user has to check all the places that data exists. Forgetting to change the updates can cause data inconsistency. Sometimes, it is necessary to store data according to conditions. Applying constraints is also hard with a file management system. A file management system is more suitable for a small organization to deal with the small number of clients. 5
- 6. What is difference between DBMS and File Management System? 6 DBMS vs File Management System DBMS is a software for creating and managing databases that provides a systematic way to create, retrieve, update and manage data. A file management system is a software that manages data files in a computer system. Data Redundancy Data redundancy is low in a DBMS. In a file management system, data redundancy is high. Consistency In DBMS, the data consistency is high. Data consistency is low in the file management system. Data Sharing Sharing data is easier in DBMS. Sharing data is harder in file management system. Integrity Data integrity is high in DBMS. In file management system, the data integrity is low. Operations Updating, searching, retrieving data is easier in DBMS because of queries. Updating, searching, retrieving data is harder in a file management system. Security In DBMS, the data is more secure. Data is not very secure in file management system. Backup and Recovery Process Backup and recovery process is complex in a DBMS. Backup and recovery process is simple in a file system. Number of Users DBMS is suitable for large organizations to support multiple users. File management system is suitable for small organizations or single users.
- 7. Data Model: Data Model gives us an idea that how the final system will look like after its complete implementation. It defines the data elements and the relationships between the data elements. Data Models are used to show how data is stored, connected, accessed and updated in the database management system. Here, we use a set of symbols and text to represent the information so that members of the organisation can communicate. Though there are many data models being used nowadays but the Relational model is the most widely used model. Apart from the Relational model, there are many other types of data models. 7
- 8. Data Model Categories: Hierarchical Model Network Model Entity-Relationship Model Relational Model Object-Oriented Data Model Object-Relational Data Model Semi-Structured Data Model 8
- 9. Hierarchical Data Model: • Hierarchical Model was the first DBMS model. This model organises the data in the hierarchical tree structure. The hierarchy starts from the root which has root data and then it expands in the form of a tree adding child node to the parent node. This model easily represents some of the real-world relationships like food recipes, sitemap of a website etc. Example: We can represent the relationship between the shoes present on a shopping website in the following way: Fig.: Hierarchical Model 9
- 10. Network Data Model: • This model is an extension of the hierarchical model. It was the most popular model before the relational model. This model is the same as the hierarchical model, the only difference is that a record can have more than one parent. It replaces the hierarchical tree with a graph. Example: In the example below we can see that node student has two parents i.e. CSE Department and Library. This was earlier not possible in the hierarchical model. 10
- 11. Entity-Relationship Model: Entity-Relationship Model (ER Model) is a high-level data model diagram. In this model, we represent the real-world problem in the pictorial form to make it easy for the stakeholders to understand. It is also very easy for the developers to understand the system by just looking at the ER diagram. We use the ER diagram as a visual tool to represent an ER Model. ER diagram has the following three components: Entity: Entity is a real-world thing. It can be a person, place, or even a concept. Example: Teachers, Students, Course, Building, Department, etc. are some of the entities of a School Management System. Attributes: An entity contains a real-world property called attribute. This is the characteristics of that attribute. Example: The entity teacher has the property like teacher id, salary, age, etc. Relationship: Relationship tells how two entites are related. Example: Teacher works for a department. 11
- 12. Entity-Relationship Model(contd..): Here, the entities are Teacher and Department. The attributes of Teacher entity are Teacher_Name, Teacher_id, Age, Salary, Mobile_Number. The attributes of entity Department entity are Dept_id, Dept_name. The two entities are connected using the relationship. Here, each teacher works for a department. 12 Teacher Department Works for Teacher_id Teacher_Name Dept._id Dept._name Mobile_no Address
- 13. Relational Model: Relational Model is the most widely used model. In this model, the data is maintained in the form of a two-dimensional table. All the information is stored in the form of tuples and attributes. The basic structure of a relational model is tables. So, the tables are also called relations in the relational model. Example: In this example, we have an Employee table. 13 Fig.: Employee Table
- 14. Object Oriented Model: The real-world problems are more closely represented through the object-oriented data model. In this model, both the data and relationship are present in a single structure known as an object. We can store audio, video, images, etc. in the database which was not possible in the relational model(although you can store audio and video in relational database, it is advised not to store in the relational database). In this model, two are more objects are connected through links. We use this link to relate one object to other objects. 14
- 15. Summary: What is Data? What is DBMS? What is the goal of DBMS? What is file? What are the advantages of DBMS over file management system? What is data model? Types of Data Models. 15
- 16. Thank you Drop your query at ipsita.saha@gnit.ac.in 16