Introduction to Databases Ashima wadhwa Lesson 1 Introduction to Databases Ashima wadhwa GIBS/DBMS/L1

Objectives Characteristics of file-based systems. Problems with file-based approach. Meaning of the term database. Some common uses of database systems. Meaning of the term Database Management System (DBMS). GIBS/DBMS/L1

File-Based Systems A file system is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems may use a storage device such as a hard disk or CD-ROM and involve maintaining the physical location of the files. Each program defines and manages its own data. Characteristics of File Processing System : It is a group of files storing data of an organization. • Each file is independent from one another. • Each file is called a flat file. • Each file contained and processed information for one specific function, such as accounting or inventory. • Files are designed by using programs written in programming languages such as COBOL, C, C++. GIBS/DBMS/L1

Disadvantages of simple file system Separation and isolation of data Each program maintains its own set of data. Users of one program may be unaware of potentially useful data held by other programs. Duplication of data Same data is held by different programs. Wasted space and potentially different values and/or different formats for the same item. GIBS/DBMS/L1

Disadvantages of simple file system Data dependence File structure is defined in the program code. Incompatible file formats Programs are written in different languages, and so cannot easily access each other’s files. Fixed Queries/Proliferation of application programs Programs are written to satisfy particular functions. Any new requirement needs a new program. GIBS/DBMS/L1

Need of Database Approach Arose because: Definition of data was embedded in application programs, rather than being stored separately and independently. No control over access and manipulation of data beyond that imposed by application programs. Result: the database and Database Management System (DBMS). Case Study In case of college database, there may be the number of applications like General Office, Library, Account Office, Hostel etc. There are some common data items of the student which has to be mentioned in each application, like Rollno, Name, Class, Father_Name, Address, Phone_No, Date_of_birth etc. which are stored repeatedly in file system in each application. It will cause the problem of redundancy which results in wastage of storage space and difficulty in maintenance. So, we should look for a solution to these types of redundancies. The database approach discussed below will help us to provide the solution for above problems. GIBS/DBMS/L1

Database Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. System catalog (metadata) provides description of data to enable program–data independence. Logically related data comprises entities, attributes, and relationships of an organization’s information. GIBS/DBMS/L1

Database Management System (DBMS) A software system that enables users to define, create, maintain, and control access to the database. (Database) application program: a computer program that interacts with database by issuing an appropriate request (SQL statement) to the DBMS. GIBS/DBMS/L1

Database Users Database administrators: Database Designers: Responsible for authorizing access to the database, for coordinating and monitoring its use, acquiring software and hardware resources, controlling its use and monitoring efficiency of operations. Database Designers: Responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end-users and understand their needs. GIBS/DBMS/L1

Categories of End-users End-users: They use the data for queries, reports and some of them update the database content. End-users can be categorized into: A) Casual Users B) Naïve Users C) Sophisticated end Users D) Standalone Users Casual: access database occasionally when needed Naïve or Parametric: they make up a large section of the end-user population. They use previously well-defined functions in the form of “canned transactions” against the database. Examples are bank-tellers or reservation clerks who do this activity for an entire shift of operations. GIBS/DBMS/L1

Characteristics of DBMS Self Describing Nature of a Database System Insulation between Program and Data Data Abstraction Support of Multiple Views of the Data Sharing of Data and Multi User Transaction Processing GIBS/DBMS/L1

Advantages of DBMS Controlling Redundancy Restricting Unauthorized Access Providing Persistent Storage for Program Objects Providing Storage Structure for Efficient Query Processing Providing Backup and Recovery Providing Multiple User Interface Representing complex Relationship among data Enforcing Integrity Constraints Reduced Application Development time Flexibility GIBS/DBMS/L1

Objectives of DBMS Share ability Availability Evolve ability Adaptability Integrity Data Security Data Independence Redundancy Control Avoidance of Inconsistency GIBS/DBMS/L1

Share ability: An ability to share data resources is a fundamental objective of database management. In its fullest interpretation, this means different people and different processes using the same actual data at virtually the same time. Share ability advatages: Serving differently types of users with varying skill levels - Handling different user views of the same stored data. - Combining interrelated data - Setting standards - Controlling concurrent updates so as to maintain data integrity - Coordinating restart and recovery operations across multiple users. GIBS/DBMS/L1

Availability: Availability means bringing the data of an organization to the users of that data. They system which manages data resources should be easily accessible to the people within n organization – making the data available when and where it is needed, and in the manner and form in which it is needed. Availability refers to both the data and the DBMS which delivers the data. Availability functions make the database available to users: defining and creating a database, and getting data in and out of a database. These are the direct functions performed by a DBMS. A DBMS should accommodate diversity in the data stored. GIBS/DBMS/L1

Evolve ability: Evolve ability refers to the ability of the DBMS to change in response to growing user needs and advancing technology. Evolve ability is the system characteristic that enhances future availability of the data resources. A system exhibiting adaptive behavior actively seeks a particular state or goal by changing itself in response to a change in itself or its environment. Evolvability implies the gradual unfolding, development and growth of a system to better meet the needs of the using environment: and it implies change of the system in response to changing needs and technology GIBS/DBMS/L1

Adaptability : Adaptability is a more advanced form of evolve ability in which built in algorithms enable a system to change itself, rather than having a change made to it. Adaptability involves purposive, self organizing, or self controlling behavior, that is, self regulation toward a single criterion of success: ultimate, long-term survival. GIBS/DBMS/L1

Integrity: The importance and pervasiveness of the need to maintain database integrity is rooted in the reality that man is perfect. Destruction, errors and improper disclosure must be anticipated and explicit mechanisms provided for handling them. The three primary facets of database integrity are:- protecting the existence of the database Maintaining the quality of the database Ensuring the privacy of the database. In Database management system, data in database is stored in tables. A single database contains multiple tables and relationships can be created between tables (or associated data entities). This makes easy to retrieve and update data. GIBS/DBMS/L1

Data Security : Form is very important object of DBMS. You can create forms very easily and quickly in DBMS. Once a form is created, it can be used many times and it can be modified very easily. The created forms are also saved along with database and behave like a software component which are password protected. GIBS/DBMS/L1

Data Independence : The separation of data structure of database from the application program that uses the data is called data independence. In DBMS, you can easily change the structure of database without modifying the application program. GIBS/DBMS/L1

Redundancy Control : In non-database systems each application program has its own private files. In this case, the duplicated copies of the same data is created in many places. In DBMS, all data of an organization is integrated into a single database file. The data is recorded in only one place in the database and it is not duplicated. GIBS/DBMS/L1

Avoidance of Inconsistency : By controlling the data redundancy, the data consistency is obtained. If a data item appears only once, any update to its value has to be performed only once and the updated value is immediately available to all users. If the DBMS has controlled redundancy, the database system enforces consistency. GIBS/DBMS/L1

Questions ? GIBS/DBMS/L1