Database Management system intro.pptx

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1. Unit 1 Database Basics, Data Flow Diagram and ER Model: Introduction – Database System – Characteristics of Database Management Systems – Database Management System Architecture – Database Models – Data Flow Diagram – ER Model Relational Algebra and Normal Forms: Introduction – Flat – File Database – Relational Database Model – Structure of Relational Model – Keys – Relational Algebra – Normalization – Functional Dependency -First Normal Form – Second Normal Form – Third Normal Form – BCNF – Forth Normal Form.

2. Introduction A  database  is an organized collection of data that allows for easy access and management. Think of it as a digital repository where you can store and retrieve information efficiently. Data within a database can take various forms, including text, numbers, media files, and more. The term “data” originates from the word “datum,” which refers to a single piece of information

3. A Database Management System (DBMS) is a software package used to create and manage databases. DBMS provides an interface to perform various operations like database creation, storing data in it, updating data, creating a table in the database and a lot more. It provides protection and security to the database. In the case of multiple users, it also maintains data consistency. Example: Microsoft SQL server, MongoDB, MySQL, Oracle

4. Database System/History/Types of DBMS/Data models Database systems and development of applications to process the stored data have evolved over the years. In early 1960’s magnetic tapes were used for storage and processing of data. They were sequential in nature and data processing related applications were very limited. In the late 1960’s, emergence of hard disks changed the scenario of data processing greatly. With hard disks data could be accessed directly and limitation of sequential access was over. Database related applications improved with the invention of hard disks.

5. Network and hierarchical data models were also developed in this era. These data models were quite popular till late 1970s. Hardware gradually improved and the process is continuing. In late 1980’s the hard disk space that was thought to be sufficient is now available in main memory. At present servers with 1 GB to 8 GB main memory is quite common. Hard disk space in servers are of the order of 1000 GBs. Relational Database Management Software (RDBMS) also evolved and dominated the market. Lots of Graphics User Interface (GUI) based software are available for the development of very sophisticated database applications. Current trend is object oriented relational database system .

6. 1. Hierarchical Model The hierarchical database model organizes data into a  tree-like structure , with a  single root , to which all the other data is linked. The hierarchy starts from the  Root  data, and expands like a tree, adding  child  nodes to the  parent  nodes. In this model, a child node will only have a  single parent node . This model efficiently describes many real-world relationships like the  index of a book , 

7. 2. Network Model The Network Model is an extension of the Hierarchical model. In this model, data is organized more like a  graph , and allowed to have  more than one parent node . In the network database model, data is  more related  as more relationships are established in this database model. Also, as the data is more related, hence  accessing the data is also easier  and  fast .

8. 3. Entity-relationship Model In this database model, relationships are created by dividing objects of interest into entities and their characteristics into attributes. Different entities are related using  relationships . ER Models are defined to represent the relationships in pictorial form to make it easier for different stakeholders to understand. This model is good to design a database, which can then be turned into tables in a relational model .

9. 4. Relational Model In this model, data is organized in two-dimensional  tables  and the relationship is maintained by storing a common field. This model was introduced by  E.F Codd  in 1970, and since then it has been the most widely used database model. The basic structure of data in the relational model is  tables . All the information related to a particular type is stored in  rows  of that table. Hence, tables are also known as  relations  in the relational model.

10. 5. Object-oriented Model In this model, data is stored in the form of objects. The behavior of the object-oriented database model is just like object-oriented programming. A very popular example of an Object Database management system or  ODBMS  is  MongoDB  which is also a NoSQL database. This database model is not mature enough as compared to the relational database model.

11. ADVANTAGES OF DBMS 1. Centralized management and control over the data: All controls related to the database are done from a central place. The role of a Database Administrator (DBA) is very important. The DBA creates users and assign privileges to them. The DBA is also responsible for creation, deletion, modification and fine-tuning of the database and all other database maintenance related jobs.

12. 2. Sharing of database and elimination of redundant operation The data stored in database are shared among different applications. Consider a scenario of an automated office where all applications are developed based on some database. All applications related to the automation essentially require sharing of common data of each employee. If the data is available in some tables, it should be available to all other applications. The applications related to database should be developed so that redundancy in data storage and redundancy in data entry is totally eliminated.

13. 3. Security Security of data is of prime importance. All database management software incorporate security features in some form or other. Security of data ensures that only the authorized user is allowed to access relevant data. Security of data also addresses the problems related to virus attack and safety of data during transmission from one place to other.

14. 1.2.2 Disadvantages of Database Management System 1.Implementation cost The first time implementation cost of database related application is very high. The major implementation costs are related to software, hardware and application development. It ranges right from few lakhs to crores of rupees and depends on the target requirements and type of application.

15. 2. Maintenance cost Even after implementation of database application, its maintenance cost is quite high. Maintenance cost is mainly due to day-to-day data entry, modification of application, creation of database, backup, recovery and fine-tuning of the databases.

16. 1.3 CHARACTERISTIC OF DATABASE MANAGEMENT SYSTEM 1.3.1 Data Representation Data representation is divided into two parts: high-level details and low-level details. The high-level view of data represents information related to the table, number of records in the table and attributes that form the record. The low-level details deal with the physical storage of data.

17. 1.3.2 Performance The performance of a DBMS is determined by its response time. The type of physical storage and memory do effect response time. In any database, data should be stored in such a manner that they can be accessed quickly and conveniently. 1.3.3 Integrity When large number of users concurrently uses a database, the data items and associations between them must not be destroyed. A unit of activity must be either completed or appear to never have started. Storage, insertion, updation and deletion of data have to be performed in such a fashion that the system can recover from hardware failure, if any.

18. 1.3.4 Minimal Redundancy The redundant data consume a lot of memory space. They also lead to problems related to insertion, updation , deletion and inconsistency. DBMS should therefore, eliminate redundancy wherever possible. 1.3.5 Privacy The privacy of DBMS implies that individuals and corporation, as a whole should have a due right to determine themselves when, how and to what extent information available with them is to be transmitted to others.

19. 1.3.6 Security The security of data means protecting data against accidental or intentional disclosure to unauthorized persons. It also implies unauthorized modification or destruction. The DBMS should include mechanism to authenticate users to access data as per their authorization.

20. 1.4 DATABASE MANAGEMENT SYSTEM ARCHITECTURE The architecture of database management system is based on three-schema architecture, which is based on different levels of abstraction. The three levels of database architecture are internal, conceptual and external. 1.4.1 Internal Level The internal level is also known as physical level database architecture. It is mainly concerned with the methodology through which the data is stored physically. It describes the complete details related to physical data storage and access paths.

21. 1.4.2 Conceptual Level The conceptual level is also known as logical level database architecture. It hides the details of physical storage from the developer and user of the database. It mainly describes entities, data types, relationships, constraints and other details. 1.4.3 External Level The external level is also known as view level database architecture. It is concerned with the way data will be viewed by a user.

22. 1.9 Data Flow diagram The Data Flow Diagrams (DFD) are the most commonly used way of documenting the process of system design. They are a pictorial way of showing the flow of data into, around and out of a system. DFDs do not give detailed descriptions of modules, but graphically describe a system’s data and how the data interact with the system. DFDs are constructed using four major components viz. Process data flow external entity data stores

23. The DFD is also known as bubble chart. It comprises only four types of components and is simple to use. It is used to provide the end user with a physical idea of flow of data.

24. 1.9.1 Process The first component of the DFD is known as a process. It is also known as a bubble, a function, or a transformation. Process represent activity transforms the input data into output data, i.e. it shows how one or more inputs are changed into outputs. The process is represented graphically as a circle. Some systems analysts prefer to use an oval to represent a process. A good process name usually consists of a verb and an object, i.e. an active verb and an object to form a descriptive phrase of the process. Examples of process names are VALIDATE DATA, COMPUTE INCOME TAX, CALCULATE TRAJECTORY and similar to that. Diagrammatically a process is shown in Figure 1.2.

25. 1.9.2 Data Flow The data flow is used to describe the movement of information from one part of the system to another part. Thus, the flows represent data in motion. The data flow shows direction using an arrowhead at either ends of the flow. It indicates whether the data are moving into or out of a process or doing both. A flow is represented graphically by an arrow as shown in Figure 1.2. 1.9.3 External Entities The external entities represent the source of data as input to the system. They are also the destination of system data. These are represented by rectangle as shown in Figure 1.2

26. 1.9.4 Data Stores The data stores represent stores of data within the system. The store is used to model a collection of data at rest. The notation for a store is two parallel lines as shown in Figure 1.2. Example: In this example preparation of chowmein with the help of DFD is demonstrated. Three levels of DFD are shown in Figures 1.3 to 1.5. Figure 1.3 represents the context diagram (or DFD level 0), which has got 11 inputs and 1 output.

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28. Figure 1.4 represents DFD level 1. In this level there are three processes viz. ‘boil noodles’, ‘prepare vegetables’ and ‘prepare chowmein ’. Note that no new inputs are included in this level of DFD. The input ‘Oil’ is used in ‘boil noodles’ as well as in ‘prepare vegetables’.

29. The process ‘prepare vegetables’ in DFD level 1 is broken into ‘chop the vegetables’ and ‘ saute chopped vegetables’ in DFD level 2 (Figure 1.5). Figure 1.5 Data flow diagram level 2.

30. DFD for Library management system Level 0 DFD

31. DFD for Hotel Management System

32. 1.10 Entity Relationship Diagram