FCC134 Chapter 1 Introduction to Database.pdf

INTRODUCTION TO DATABASE INTRODUCTION TO DATABASE MANAGEMENT SYSTEM Learning Outcome: Basic Definitions and Concepts: ▪ Data ▪ Information ▪ Meta Data ▪ Data Dictionary ▪ Database ▪ Database Management System (DBMS) ▪ Characteristics of DBMS ▪ Application of DBMS 1. Data Data is raw fact or figur...

INTRODUCTION TO DATABASE INTRODUCTION TO DATABASE MANAGEMENT SYSTEM Learning Outcome: Basic Definitions and Concepts: ▪ Data ▪ Information ▪ Meta Data ▪ Data Dictionary ▪ Database ▪ Database Management System (DBMS) ▪ Characteristics of DBMS ▪ Application of DBMS 1. Data Data is raw fact or figures or entity. Data Facts, figures, statistics etc. having no particular meaning Data is nothing but facts and statistics stored or free flowing over a network, generally it's raw and unprocessed. When activities in the organization takes place, the effect of these activities need to be recorded which is known as Data. 2. Information Data becomes information when it is processed, turning it into something meaningful. Processed data is called information The purpose of data processing is to generate the information required for carrying out the business activities. Information is the result of processing raw data to reveal its meaning. Data processing can be as simple as organizing data to reveal patterns or as complex as making forecasts or drawing inferences using statistical modeling. What is Information? Data and information are closely related and are often used interchangeably. Information is nothing but refined data. In other way, we can say, that information is processed, organized or summarized data. According to Burch et. al., “Information is data that have been put into a meaningful and useful content and communicated to a recipient who uses it to made decisions”. Information consists of data, images, text, documents and voice, but always in a meaningful content. What is Information? Data are processed to create information. The recipient receives the information and then makesa decision and takes an action, which may trigger other actions as show in Figure 1. What is Information? To reveal meaning, information requires context. For example, an average temperature reading of 105 degrees does not mean much unless you also know its context: Is this reading in degrees Fahrenheit or Celsius? Is this a machine temperature, a body temperature, or an outside air temperature? Information can be used as the foundation for decision making.  Three Major Key Attributes of Information In these days, there is no lack of data, but there is lack of quality information. The quality information means information that is: 1. Accurate 2. Timely 3. Relevant which are the three major key attributes of information. 1.1 Accurate It means that the information is free from errors, and it clearly and accurately reflects the meaning of data on which it is based. It also means it is free from bias and conveys an accurate picture to the recipient. 1.2 Timely It means that the recipients receive the information when they need it and within the required time frame. 1.3 Relevancy It means the usefulness of the piece of information for the corresponding persons. It is a very subjective matter. Some information that is relevant for one person might not be relevant for another and vice versa e.g., the price of printer is irrelevant for a person who wants to purchase computer. Three Major Key Attributes of Information So, organization that have good information system, which produce information that is accurate, timely and relevant will survive and those that do not realize the importance of information will soon be out of business. 2. Meta Data A meta data is the data about the data. The meta data describe objects in the database and makes easier for those objects to be accessed or manipulated. The meta data describes the database structure, sizes of data types, constraints, applications, autorisation etc., that are used as an integral tool for information resource management. For example, the metadata component stores information such as the name of each data element, the type of values (numeric, dates, or text) stored on each data element, and whether the data element can be left empty. 2. 1 Meta Data 2.2 Meta Data There are three main types of meta data: 1. Descriptive meta data 2. Structural meta data 3. Administrative meta data. 2.3 Descriptive meta data It describes a resource for purpose such as discovery and identification. In a traditional library cataloging that is form of meta data, title, abstract, author and keywords are examples of meta data. 2.4 Structural meta data It describes how compound objects are put together. The example is how pages are ordered to form chapters. 2.5 Administrative meta data It provides information to help manage a resource, such as when and how it was created, file type and other technical information, and who can access it. There are several subsets of data. 3 Data Dictionary The data dictionary contains information of the data stored in the database and is consulted by the DBMS before any manipulation operation on the database. It is an integral part of the database management systems and store meta data i.e., information about the database, attribute names and definitions for each table in the database. It helps the DBA in the management of the database, user view definitions as well as their use. 3.1 Data Dictionary 3.2 Data Dictionary Data dictionary is generated for each database and generally stores and manages the following types of information : The complete information about physical database design e.g., storage structures, access paths and file sizes etc. The information about the database users, their responsibilities and access rights of each user. The complete information about the schema of the database. 3.2 Data Dictionary The high-level descriptions of the database transactions, applications and the information about the relationships of users to the transactions. The information about the relationship between the data items referenced by the database transactions. This information is helpful in determining which transactions are affected when some data definitions are modified. The data dictionaries are of two types: 1. Active data dictionary 2. Passive data dictionary. 3.3 Active data dictionary It is managed automatically by the database management system (DBMS) and are always consistent with the current structure and definition of the database. Most of the RDBMS’s maintain active data dictionaries. 3.4 Passive data dictionary It is used only for documentation purposes and the data about fields, files and people are maintained into the dictionary for cross references. It is generally managed by the users of the system and is modified whenever the structure of the database is changed. The passive dictionary may not be consistent with the structure of the database, since modifications are performed manually by the user. It is possible that passive dictionaries may contain information about organisational data that is not computerized as these are maintained by the users. 4. Database A database is a collection of interrelated data stored together with controlled redundancy to serve one or more applications in an optimal way. The data are stored in such a way that they are independent of the programs used by the people for accessing the data. The approach used in adding the new data, modifying and retrieving the existing data from the database is common and controlled one. A database may be generated and maintained manually, or it may be computerized. 4. Database The database is a collection of inter-related data which is used to retrieve, insert and delete the data efficiently. It is also used to organize the data in the form of a table, schema, views, and reports, etc. Using the database, you can easily retrieve, insert, and delete the information. For example: The college Database organizes the data about the admin, staff, students and faculty etc. 4. Database 4. Database It is also defined as a collection of logically related data stored together that is designed to meet information requirements of an organization. We can also define it as an electronic filling system. The example of a database is a telephone directory that contains names, addresses and telephone numbers of the people stored in the computer storage. Databases are organized by: 1. Fields, 2. Records 3. Files 4.1 Fields It is the smallest unit of the data that has meaning to its users and is also called data item or data element. Name, Address and Telephone number are examples of fields. These are represented in the database by a value. 4.1 Fields 4.2 Records A record is a collection of logically related fields, and each field is possessing a fixed number of bytes and is of fixed data type. Alternatively, we can say a record is one complete set of fields and each field have some value. The complete information about a particular phone number in the database represents a record. Records are of two types fixed length records and variable length records. 4.2 Records 4.3 Files A file is a collection of related records. Generally, all the records in a file are of same size and record type but it is not always true. The records in a file may be of fixed length or variable length depending upon the size of the records contained in a file. The telephone directory containing records about the different telephone holders is an example of file. Components of a Database Components of a Database 1. Data item: It is defined as a distinct piece of information. 2. Relationships: It represents a correspondence between various data elements. 3. Constraints: Are used to limit the type of data that can go into a table. 4. Schema: It describes the organization of data and relationships within the database. Components of a Database The schema consists of definitions of the various types of record in the database, the data-items they contain and the sets into which they are grouped. The storage structure of the database is described by the storage schema. The conceptual schema defines the stored data structure. The external schema defines a view of the database for particular users. Components of a Database 5. Database Management System (DBMS) DBMS is a program or group of programs that work in conjunction with the operating system to create, process, store, retrieve, control and manage the data. It acts as an interface between the application program and the data stored in the database. A DBMS is a collection of program that enables user to create and maintain a database. The DBMS is hence a general-purpose software system that facilitates the process of defining constructing and manipulating database for various applications. 5. Database Management System (DBMS) DBMS is the software designed to store, manage, and facilitate access to large collections of related data. The combination of a DBMS and a database is then often called a database system. The management system is important because without the existence of some kind of rules and regulations it is not possible to maintain the database. 5. Database Management System (DBMS) We have to select the particular attributes which should be included in a particular table; the common attributes to create relationship between two tables; if a new record has to be inserted or deleted then which tables should have to be handled etc. These issues must be resolved by having some kind of rules to follow in order to maintain the integrity of the database. Database systems are designed to manage large bodies of information. Management of data involves both defining structures for storage of information and providing mechanisms for the manipulation of information. 5. Database Management System (DBMS) In general data management consists of following tasks: 1. Data capture: Which is the task associated with gathering the data as and when they originate. 2. Data classification: Captured data has to be classified based on the nature and intended usage. 3. Data storage: The segregated data has to be stored properly. 4. Data arranging: It is very important to arrange the data properly 5. Data retrieval: Data will be required frequently for further processing; Hence it is very important to create some indexes so that data can be retrieved easily. 5. Database Management System (DBMS) 6. Data maintenance: Maintenance is the task concerned with keeping the data UpToDate. 7. Data Verification: Before storing the data, it must be verified for any error. 8. Data Coding: Data will be coded for easy reference. 9. Data Editing: Editing means re-arranging the data or modifying the data for presentation. 10. Data transcription: This is the activity where the data is converted from one form into another. 11. Data transmission: This is a function where data is forwarded to the place where it would be used further. Characteristics of DBMS ▪ To incorporate the requirements of the organization, system should be designed for easy maintenance. ▪ Information systems should allow interactive access to data to obtain new information without writing fresh programs. ▪ System should be designed to co-relate different data to meet new requirements. ▪ An independent central repository, which gives information and meaning of available data is required. Characteristics of DBMS ▪ Integrated database will help in understanding the inter-relationships between data stored in different applications. ▪ The stored data should be made available for access by different users simultaneously. ▪ Automatic recovery feature has to be provided to overcome the problems with processing system failure. Application of DBMS Databases touch all aspects of our lives. Some of the major areas of application are as follows: 1. Banking 2. Airlines 3. Universities 4. Manufacturing and selling 5. Human resources Application of DBMS ▪ Sales: For customer, product, and purchase information. ▪ Accounting: For payments, receipts, account balances, assets and other accounting information. ▪ Human resources: For information about employees, salaries, payroll taxes, and benefits, and for generation of paychecks. ▪ Manufacturing: For management of the supply chain and for tracking production of items in factories, inventories of items in warehouses and stores, and orders for items. ▪ Online retailers: For sales data noted above plus online order tracking, generation of recommendation lists, and maintenance of online product evaluations. Application of DBMS ▪ Banking: For customer information, accounts, loans, and banking transactions. ▪ Credit card transactions: For purchases on credit cards and generation of monthly statements. ▪ Finance: For storing information about holdings, sales, and purchases of financial instruments such as stocks. Application of DBMS ▪ Universities: For student information, course registrations, and grades (in addition to standard enterprise information such as human resources and accounting). ▪ Airlines: For reservations and schedule information. Airlines were among the first to use databases in a geographically distributed manner. ▪ Telecommunication: For keeping records of calls made, generating monthly bills, maintaining balances on prepaid calling cards, and storing information about the communication networks.