Module-01 Introduction to Database Concepts

Transcription

1 Module 1 : Introduction to Database Concepts 1 Module-01 Introduction to Database Concepts 1.1 Motivation Database systems are basically developed for large amount of data. When dealing with huge amount of data provide a strong formal foundation in database concepts, technology and practice to the participants to groom them into well-informed database application developers. 1.2 Objective The main goal of this topic is to understand the basic need of database as a building block of any real life applications. 1.3 Syllabus Prerequisites Lecture Plan Syllabus Duration Self Study Introduction to databases requires that we should know about basic operations of file processing system ,1.6.3 Introduction,Characteristics of databases, Traditional File processing system 1 hour File system V/s Database system 1 hour 1.6.5,1.6.6 View of Data in DBMS,database 1 hour Instance & Schema Concerns when using an enterprise database 1.6.7,1.6.8 Data Independence 1 hour DBMS system architecture 3 hours 1.4 Definitions , Users of Database system Database Administrator 1 hour 1) Data Data is a collection of facts, such as values or measurements. It can be numbers, words, measurements, observations or even just descriptions of things. 2) Information- Information is interpreted data. When data is processed, organized, structured or presented in a given context so as to make it useful, it is called Information. 3) Database - A database is a collection of data that is organized so that it can easily be accessed, managed, and updated. 4) Database management system- A database management system(dms) is a is essentially nothing more than a computerized data-keeping system. A DMS is a software program that enables the creation and management of databases.

2 Module 1 : Introduction to Database Concepts 2 5) Data Independence Data independence is a form of database management that keeps data separated from all programs that make use of it and to restrict access to the storage structure of the data by the user applications. 6) Database Administrator- A database administrator (DBA) is a person who has central control over the system. 1.5 Course Objective, Course Outcome and Learning outcome CO1: To provide a sound introduction to the discipline of database management systems. CO1: Student should be able to learn the features of database management systems and Relational database LO: After Completion of this module, student should be able to learn the following points Difference between data and information and Knowledge Drawbacks of Traditional file processing system Evolution of Database System, its advantages and disadvantages Database users including data base administrator DBMS Architecture & Data Independence 1.6 Module theory Notations: DB: Database DBMS: Database Management System DML: Data Manipulation Language DDL: Data Definition Language DBA: Database Administrator Introduction to Data processing System: Data processing is any computer process that converts data into information. The processing is usually assumed to be automated and running on a computer. Because data are most useful when wellpresented and actually informative, data-processing systems are often referred to as information systems to emphasize their practicality. Data processing systems typically manipulate raw data into information, and likewise information systems typically take raw data as input to produce information as output

3 Module 1 : Introduction to Database Concepts 3 Fig.1.1 Data Processing Diagram Traditional File processing system: File processing systems was an early attempt to computerize the manual filing system that we are all familiar with. 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. In the traditional approach, we used to store information in flat files which are maintained by the file system under the operating system's control. Here, flat files are files containing records having no structured relationship among them. The file handling which we learn under C/C ++ is the example of file processing system. The Application programs written in C/C ++ like programming languages go through the file system to access these flat. files as shown. Characteristics of file processing system: Fig 1.2 Traditional 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.

4 Module 1 : Introduction to Database Concepts 4 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++. The physical implementation and access procedures are written into database application; therefore, physical changes resulted in intensive rework on the part of the programmer. As systems became more complex, file processing systems offered little flexibility, presented many limitations, and were difficult to maintain. Limitations of the File Processing System: There are following problems associated with the File Based Approach: 1. Separated and Isolated Data: To make a decision, a user might need data from two separate files. First, the files were evaluated by analysts and programmers to determine the specific data required from each file and the relationships between the data and then applications could be written in a programming language to process and extract the needed data. Imagine the work involved if data from several files was needed. 2. Duplication of data: Often the same information is stored in more than one file. Uncontrolled duplication of data is not required for several reasons, such as: Duplication is wasteful. It costs time and money to enter the data more than once It takes up additional storage space, again with associated costs. Duplication can lead to loss of data integrity; in other words the data is no longer consistent. 3. Data Dependence: In file processing systems, files and records were described by specific physical formats that were coded into the application program by programmers. If the format of a certain record was changed, the code in each file containing that format must be updated. Furthermore, instructions for data storage and access were written into the application's code. Therefore,.changes in storage structure or access methods could greatly affect the processing or results of an application. 4. Difficulty in representing data from the user's view: To create useful applications for the user, often data from various files must be combined. In file processing it was difficult to determine relationships between isolated data in order to meet user requirements. 5. Data Inflexibility: Program-data interdependency and data isolation, limited the flexibility of file processing systems in providing users with ad-hoc information requests 6. Incompatible file formats: As the structure of files is embedded in the application programs, the structures are dependent on the application programming language. For example, the structure of a file generated by a COBOL program may be different from the structure of a file generated by a 'C' program. The direct incompatibility of such files makes them difficult to process jointly.

5 Module 1 : Introduction to Database Concepts 5 7. Data Security. The security of data is low in file based system because, the data is maintained in the flat file(s) is easily accessible. For Example: Consider the Banking System. The Customer Transaction file has details about the total available balance of all customers. A Customer wants information about his account balance. In a file system it is difficult to give the Customer access to only his data in the file. Thus enforcing security constraints for the entire file or for certain data items are difficult. 8. Transactional Problems. The File based system approach does not satisfy transaction properties like Atomicity, Consistency, Isolation and Durability properties commonly known as ACID properties. 9. Concurrency problems. When multiple users access the same piece of data at same interval of time then it is called as concurrency of the system. When two or more users read the data simultaneously there is ll( problem, but when they like to update a file simultaneously, it may result in a problem. 10. Poor data modeling of real world. The file based system is not able to represent the complex data and interfile relationships, which results poor data modeling properties Database Management System: To overcome all drawbacks of file processing system, a new system called database system is developed. All the files in the file processing system are known as tables in the database. The contents of files form records of the table. In database, each of column values are known as attribute and each row of information is known as record. There no difference in the data being stored. But it is different from the file system by the way data is stored and accessed in the database. A DBMS is software that allows creation, definition and manipulation of database. DBMS is actually a tool used to perform any kind of operation on data in database. DBMS also provides protection and security to database. It maintains data consistency in case of multiple users. Here are some examples of popular DBMS are MySql, Oracle, Sybase, Microsoft Access and IBM DB2 etc. Basic Components of Database System: The database system can be divided into four components.

6 Module 1 : Introduction to Database Concepts 6 Fig 1.4 Components of Database System Users: Users may be of various type such as DB administrator, System developer and End users. Database application : Database application may be Personal, Departmental, Enterprise and Internal DBMS: Software that allow users to define, create and manages database access, Ex: MySql, Oracle etc. Database: Collection of logical data. Advantages of DBMS over File Processing System: DBMS is developed to cover the drawbacks of the traditional file system. 1. Data Mapping and Access: - DBMS defines the way to map any two related tables by means of primary key foreign key relationship. Primary key is the column in the table which responsible for uniquely identifying each record in the table. Foreign key is the column in the table which is a primary key in other table and with which the entries in the current table are related to other table. For example, in the new database system, we can Student and Student_Report table as follows.

7 Module 1 : Introduction to Database Concepts 7 STUDENT_ID is the unique using which we can identify each student and hence it forms a primary key in STUDENT table. Similarly, REPORT_ID is the primary key in the STUDENT_REPORT table. STUDENT_ID in the STUDENT_REPORT table is the foreign key. It links STUDENT and STUDENT_REPORT tables. Because of such mapping, it becomes each for the programmer to search for related tables, join them, and fire the query as per the requirement. This reduces the time consumed while searching and mapping these tables. Even when there is large amount of data, the time consumed to retrieve, insert, update or delete is very less. Hence there is no data isolation in the system. 2. Data Redundancy: - By the introduction of primary key in the table, data redundancy problem is reduced to great extent. As we saw, primary key is the unique column for each record, when there is a re-entry of same record, it does not allow saving such records. DBMS has strong designing techniques like normalization which makes sure the same copy of data is not stored in same table or in multiple tables. It makes sure all the informations are stored only once in the database tables. We can see the difference in the way data is being stored in the file and database system. Primary key, foreign keys are defined; unnecessary columns are removed from the STUDENT_REPORT table in the database system. These are missing in the file processing system. 3. Data Independence and Consistency: - DBMS defines a standard to represent the data in the form of rows and columns. It also stores the information about the tables, columns, keys, storage space, used space, available space etc separately from the logical data. Hence they totally independent of the way they are stored and the data being stored. Any changes to the physical storage (like disks, tapes etc) or structure, does not harm the data being stored. Since DBMS defines each columns and rows at the beginning itself and controls the way data being entered, there is no affect on the programs or any other tables or data. Hence the consistency of the data also maintained. If there is a change in the address of any student, we just have to update it in the Student table. There is no other place his information is being stored. Hence it maintains the consistent data in the database.

8 Module 1 : Introduction to Database Concepts 8 Suppose there is a new column addition to STUDENT table, say DOB. This will change the metadata to reflect additional column in the table structure. It will hardly affect the application unless until there is a new requirement to have transaction with DOB. Hence data independence is also assured in the database. 4. Security: - DBMS allows different levels of access to different users based on their roles. In the school database, individual students will have access to their data alone, while their teachers will have access to all the students whom they are teaching and for the subjects that they are teaching. Class teacher will be able to see the reports of all the students in that class, but not other classes. Similarly, in a banking system, individual account holder will have Read-Only access to their account. While accountant can update, individual account details for each of their transaction. All these levels of security and access are not allowed in file system. 5. Integrity: - DBMS allows having restrictions on individual columns. It would be defined while designing the table itself. If we want to enter salary of an employee within the range to 40000, we can impose this while designing the table by using CHECK constraint. When salary is entered, it will automatically check for the range specified. 6. Atomicity: - DBMS makes sure either the transaction is fully complete or it is rolled back to the previous committed state. It does not allow the system to be in a partially committed state. In our example above, DBMS commits marks change transaction before calculating the total. If there is any crash or shutdown of the system, before committing the marks, then updated marks will be rolled back to the original marks. Hence it makes sure atomicity of the transaction is achieved. 7. Concurrent Access: - DBMS provide access to multiple users to access the database at the same time. It has its own mechanism to have concurrency accesses and hence avoid any incorrect data in the system. Differences between a DBMS and a file-processing system: Sr.NO. DBMS File Processing System 1. A database management system coordinates both the physical and the logical access to the data 2. A database management system reduces the amount of data duplication by ensuring that a physical piece of data is available to all programs authorized to have access to it 3. A database management system is designed to allow flexible access to data (i.e., queries) 4. A database management system is designed to coordinate multiple users accessing the same data at the same time. File-processing system coordinates only the physical access. Data written by one programing a file-processing system may not be readable by another program. File-processing system is designed to allow predetermined access to data (i.e., compiled programs). A file-processing system is usually designed to allow one or more programs to access different data files at the same time. In a file-processing system, a file can be accessed by

9 Module 1 : Introduction to Database Concepts 9 two programs concurrently only if both programs have read-only access to the file View of Data in DBMS: Abstraction is one of the main features of database systems. Hiding irrelevant details from user and providing abstract view of data to users, helps in easy and efficient user-database interaction. To understand the view of data, you must have a basic knowledge of data abstraction and instance & schema. Refer these two tutorials to learn them in detail. 1. Data abstraction 2. Instance and schema Data Abstraction in DBMS: Fig 1.5 Three Levels of data abstraction We have three levels of abstraction: 1. Physical level: This is the lowest level of data abstraction. It describes how data is actually stored in database. You can get the complex data structure details at this level. 2. Logical level: This is the middle level of 3-level data abstraction architecture. It describes what data is stored in database. 3. View level: Highest level of data abstraction. This level describes the user interaction with database system. Example: Let s say we are storing customer information in a customer table. At physical level these records can be described as blocks of storage (bytes, gigabytes, terabytes etc.) in memory. These details are often hidden from the programmers.

10 Module 1 : Introduction to Database Concepts 10 At the logical level these records can be described as fields and attributes along with their data types, their relationship among each other can be logically implemented. The programmers generally work at this level because they are aware of such things about database systems. At view level, user just interact with system with the help of GUI and enter the details at the screen, they are not aware of how the data is stored and what data is stored; such details are hidden from them Instances and Schemas: Databases change over time. The overall design of the database is called the database scheme. Design of a database is called the schema. Schema is of three types: Physical schema, logical schema and view schema. The design of a database at physical level is called physical schema, how the data stored in blocks of storage is described at this level. Three-Schema Architecture: The goal of the three-schema architecture is to separate the user applications from the physical database. In this architecture, schemas can be defined at the following three levels: 1.6 Three-Schema Architecture: 1. The internal level has an internal schema, which describes the physical storage structure of the database. The internal schema uses a physical data model and describes the complete details of data storage and access paths for the database.

11 Module 1 : Introduction to Database Concepts The conceptual level has a conceptual schema, which describes the structure of the whole database for a community of users. The conceptual schema hides the details of physical storage structures and concentrates on describing entities, data types, relationships, user operations, and constraints. Usually, a representational data model is used to describe the conceptual schema when a database system is implemented. This implementation conceptual schema is often based on a conceptual schema design in a high-level data model. 3. The external or view level includes a number of external schemas or user views. Each external schema describes the part of the database that a particular user group is interested in and hides the rest of the database from that user group. As in the previous level, each external schema is typically implemented using a representational data model, possibly based on an external schema design in a high-level data model Data Independence: A database system normally contains a lot of data in addition to users data. For example, it stores data about data, known as metadata, to locate and retrieve data easily. It is rather difficult to modify or update a set of metadata once it is stored in the database. But as a DBMS expands, it needs to change over time to satisfy the requirements of the users. If the entire data is dependent, it would become a tedious and highly complex job. Metadata itself follows a layered architecture, so that when we change data at one layer, it does not affect the data at another level. This data is independent but mapped to each other. 1. Logical Data Independence

12 Module 1 : Introduction to Database Concepts 12 Logical data is data about database, that is, it stores information about how data is managed inside. For example, a table (relation) stored in the database and all its constraints, applied on that relation. Logical data independence is a kind of mechanism, which liberalizes itself from actual data stored on the disk. If we do some changes on table format, it should not change the data residing on the disk. 2. Physical Data Independence All the schemas are logical, and the actual data is stored in bit format on the disk. Physical data independence is the power to change the physical data without impacting the schema or logical data. For example, in case we want to change or upgrade the storage system itself suppose we want to replace hard-disks with SSD it should not have any impact on the logical data or schemas. Difference between logical and physical data independence: Sr.No. Logical data independence physical data independence 1. Logical data independence means that users are shielded from changes in the logical structure of the data 2. Logical data independence Is the ability to modify the conceptual schema without having alteration in external schemas or application programs. Physical data independence insulates users from changes in the physical storage of the data. Physical data independence is the ability to modify the inner schema without having alteration to the conceptual schemas or application programs Database System Architecture: The design of a DBMS depends on its architecture. It can be centralized or decentralized or hierarchical. The architecture of a DBMS can be seen as either single tier or multi-tier. An n-tier architecture divides the whole system into related but independent n modules, which can be independently modified, altered, changed, or replaced. In 1-tier architecture, the DBMS is the only entity where the user directly sits on the DBMS and uses it. Any changes done here will directly be done on the DBMS itself. It does not provide handy tools for endusers. Database designers and programmers normally prefer to use single-tier architecture. If the architecture of DBMS is 2-tier, then it must have an application through which the DBMS can be accessed. Programmers use 2-tier architecture where they access the DBMS by means of an application. Here the application tier is entirely independent of the database in terms of operation, design, and programming.

13 Module 1 : Introduction to Database Concepts 13 Three Tier Database System Architecture: 3-tier architecture separates its tiers from each other based on the complexity of the users and how they use the data present in the database. It is the most widely used architecture to design a DBMS. Fig 1.7 Three Tier Database System Architecture Database (Data) Tier At this tier, the database resides along with its query processing languages. We also have the relations that define the data and their constraints at this level. Application (Middle) Tier At this tier reside the application server and the programs that access the database. For a user, this application tier presents an abstracted view of the database. Endusers are unaware of any existence of the database beyond the application. At the other end, the database tier is not aware of any other user beyond the application tier. Hence, the application layer sits in the middle and acts as a mediator between the end-user and the database. User (Presentation) Tier End-users operate on this tier and they know nothing about any existence of the database beyond this layer. At this layer, multiple views of the database can be provided by the application. All views are generated by applications that reside in the application tier. Multiple-tier database architecture is highly modifiable, as almost all its components are independent and can be changed independently Database System Structure: Database systems are partitioned into modules for different functions. Some functions (e.g. file systems) may be provided by the operating system. Components include: File manager manages allocation of disk space and data structures used to represent information on disk. Database manager: The interface between low-level data and application programs and queries. Query processor translates statements in a query language into low-level instructions the database manager understands. (May also attempt to find an equivalent but more efficient form.)

14 Module 1 : Introduction to Database Concepts 14 DML precompiler converts DML statements embedded in an application program to normal procedure calls in a host language. The precompiler interacts with the query processor. DDL compiler converts DDL statements to a set of tables containing metadata stored in a data dictionary. In addition, several data structures are required for physical system implementation: Data files: store the database itself. Data dictionary: stores information about the structure of the database. It is used heavily. Great emphasis should be placed on developing a good design and efficient implementation of the dictionary. Indices: provide fast access to data items holding particular values. Figure 1.8 shows these components. Fig 1.8 Database System Structure

15 Module 1 : Introduction to Database Concepts Database Users: Database users are the one who really use and take the benefits of database. There will be different types of users depending on their need and way of accessing the database. 1. Application Programmers - They are the developers who interact with the database by means of DML queries. These DML queries are written in the application programs like C, C++, JAVA, Pascal etc. These queries are converted into object code to communicate with the database. For example, writing a C program to generate the report of employees who are working in particular department will involve a query to fetch the data from database. It will include a embedded SQL query in the C Program. 2. Sophisticated Users - They are database developers, who write SQL queries to select/insert/delete/update data. They do not use any application or programs to request the database. They directly interact with the database by means of query language like SQL. These users will be scientists, engineers, analysts who thoroughly study SQL and DBMS to apply the concepts in their requirement. In short, we can say this category includes designers and developers of DBMS and SQL. 3. Specialized Users - These are also sophisticated users, but they write special database application programs. They are the developers who develop the complex programs to the requirement. 4. Stand-alone Users - These users will have stand alone database for their personal use. These kinds of database will have readymade database packages which will have menus and graphical interfaces. 5. Native Users - these are the users who use the existing application to interact with the database. For example, online library system, ticket booking systems, ATMs etc which has existing application and users use them to interact with the database to fulfill their requests Database Administrator: A database administrator (DBA) is a person who has central control over the system.the life cycle of database starts from designing, implementing to administration of it. A database for any kind of requirement needs to be designed perfectly so that it should work without any issues. Once all the design is complete, it needs to be installed. Once this step is complete, users start using the database. The database grows as the data grows in the database. When the database becomes huge, its performance comes down. Also accessing the data from the database becomes challenge. There will be unused memory in database, making the memory inevitably huge. These administration and maintenance of database is taken care by database Administrator DBA. A DBA has many responsibilities. A good performing database is in the hands of DBA.

16 Module 1 : Introduction to Database Concepts Installing and upgrading the DBMS Servers: - DBA is responsible for installing a new DBMS server for the new projects. He is also responsible for upgrading these servers as there are new versions comes in the market or requirement. If there is any failure in upgradation of the existing servers, he should be able revert the new changes back to the older version, thus maintaining the DBMS working. He is also responsible for updating the service packs/ hot fixes/ patches to the DBMS servers. 2. Design and implementation: - Designing the database and implementing is also DBA s responsibility. He should be able to decide proper memory management, file organizations, error handling, log maintenance etc for the database. 3. Performance tuning: - Since database is huge and it will have lots of tables, data, constraints and indices, there will be variations in the performance from time to time. Also, because of some designing issues or data growth, the database will not work as expected. It is responsibility of the DBA to tune the database performance. He is responsible to make sure all the queries and programs works in fraction of seconds. 4. Migrate database servers: - Sometimes, users using oracle would like to shift to SQL server or Netezza. It is the responsibility of DBA to make sure that migration happens without any failure, and there is no data loss. 5. Backup and Recovery: - Proper backup and recovery programs needs to be developed by DBA and has to be maintained him. This is one of the main responsibilities of DBA. Data/objects should be backed up regularly so that if there is any crash, it should be recovered without much effort and data loss. 6. Security: - DBA is responsible for creating various database users and roles, and giving them different levels of access rights. 7. Documentation: - DBA should be properly documenting all his activities so that if he quits or any new DBA comes in, he should be able to understand the database without any effort. He should basically maintain all his installation, backup, recovery, security methods. He should keep various reports about database performance. In order to perform his entire task, he should have very good command over DBMS Evolution of Database System: We are too used to timelines on Facebook. I thought it will be a good idea to start this article on a similar line. Following is a tree which will help you map all types of popular database management system in a timeline:

17 Module 1 : Introduction to Database Concepts 17 Fig 1.9 Evolution of Database Management System The timeline varies from 1980s to current date and is not exhaustive of all forms of data management systems. However, we will be able to cover most of the popular data management system. 1. Flat File Database: This is probably the easiest to understand but at present rarely used. You can think of this as a single huge table. Such type of datasets were used long back in 1990s, when data was only used to retrieve information in case of concerns. Very primitive analytics were possible on these databases. 2. Relational Database: Soon people starting realizing that such tables will be almost impossible to store on a longer run. The Flat File brought in a lot of redundant data at every entry. For instance, if I want to make a single data-set with all products purchased at a grocery store with all information of the customer and product, we will have every single row consisting of all customer and product information. Wherever we have a repeat product or customer, we have repeat data. People thought of storing this as different tables and define a hierarchy to access all the data, which will be called as hierarchical database. 3. Hierarchical Database is very similar to your folder structure on the laptop. Every folder can contain sub-folder and each sub-folder can still hold more sub-folders. Finally in some folders we will store files. However, every child node (sub-folder) will have a single parent (folder or sub-folder). Finally, we can create a hierarchy of the dataset :

18 Module 1 : Introduction to Database Concepts 18 Fig 1.10 Hierarchical Database Management Systems Hierarchical databases, however can solve many purposes, its applications are restricted to one-toone mapping data structures. For example, it will work well if you are using this data structure to show job profile hierarchy in a corporate. But the structure will fail if the reporting becomes slightly more complicated and a single employee reports to many managers. Hence, people thought of database structures which can have different kinds of relations. This type of structure should allow one-to-many mapping. Such table came to be known as Relational database management system (RDBMS). 4. NoSQL Database NoSQL is often known as Not Only SQL. When people realized that unstructured text carry tonnes of information which they are unable to mine using RDBMS, they started exploring ways to store such datasets. Anything which is not RDBMS today is loosely known as NoSQL. After social networks gained importance in the market, such database became common in the industry. Following is an example where it will become very difficult to store the data on RDBMS : Steps for setting up a database for a particular enterprise: Six major steps in setting up a database for a particular enterprise are: 1. Define the high level requirements of the enterprise (this step generates a document known as the system requirements specification.) 2. Define a model containing all appropriate types of data and data relationships. 3. Define the integrity constraints on the data. 4. Define the physical level. 5. For each known problem to be solved on a regular basis (e.g., tasks to be carried out by clerks or Web users) define a user interface to carry out the task, and write the necessary application programs to implement the user interface. 6. Create/initialize the database.

19 Module 1 : Introduction to Database Concepts Application of Database Management System (DBMS): 1. Railway Reservation System Database is required to keep record of ticket booking, train s departure and arrival status. Also if trains get late then people get to know it through database update. 2. Library Management System There are thousands of books in the library so it is very difficult to keep record of all the books in a copy or register. So DBMS used to maintain all the information relate to book issue dates, name of the book, author and availability of the book. 3. Banking We make thousands of transactions through banks daily and we can do this without going to the bank. So how banking has become so easy that by sitting at home we can send or get money through banks. That is all possible just because of DBMS that manages all the bank transactions. 4. Universities and colleges Examinations are done online today and universities and colleges maintain all these records through DBMS. Student s registrations details, results, courses and grades all the information are stored in database. 5. Credit card transactions For purchase of credit cards and all the other transactions are made possible only by DBMS. A credit card holder knows the importance of their information that all are secured through DBMS. 6. Social Media Sites We all are on social media websites to share our views and connect with our friends. Daily millions of users signed up for these social media accounts like facebook, twitter, pinterest and Google plus. But how all the information of users are stored and how we become able to connect to other people, yes this all because DBMS. 7. Telecommunications Any telecommunication company cannot even think about their business without DBMS. DBMS is must for these companies to store the call details and monthly post paid bills. 8. Finance Those days have gone far when information related to money was stored in registers and files. Today the time has totally changed because there are lots f thing to do with finance like storing sales, holding information and finance statement management etc. 9. Military Military keeps records of millions of soldiers and it has millions of files that should be keep secured and safe. As DBMS provides a big security assurance to the military information so it is widely used in

20 Module 1 : Introduction to Database Concepts 20 militaries. One can easily search for all the information about anyone within seconds with the help of DBMS. 10. Online Shopping Online shopping has become a big trend of these days. No one wants to go to shops and waste his time. Everyone wants to shop from home. So all these products are added and sold only with the help of DBMS. Purchase information, invoice bills and payment, all of these are done with the help of DBMS. 11. Human Resource Management Big firms have many workers working under them. Human resource management department keeps records of each employee s salary, tax and work through DBMS. 12. Manufacturing Manufacturing companies make products and sales them on the daily basis. To keep records of all the details about the products like quantity, bills, purchase, supply chain management, DBMS is used. 13. Airline Reservation system Same as railway reservation system, airline also needs DBMS to keep records of flights arrival, departure and delay status. So in short, one can say the DBMS is used everywhere around us and we cannot rely without DBMS. 1.7 Objective Type Questions: 1. Database is collection of data. a. relative b. interrelated c. different. 2. is function of database administrator. a. schema definition b. Downloading c. Network Formation 3. There are levels in database architecture. a. one b. two c. Three 4. is Database application. a. Banking b. Device switching

21 Module 1 : Introduction to Database Concepts is Database User a. Commulative b. GSM c. Naïve 6. Redundancy is a. Mismatching of Data b. Duplication of data c. Internet work Answers : b a c a c b 1.8. Short Answer Questions: 1. Define database management system Ans: Database management system (DBMS) is a collection of interrelated data and a set of programs to access those data. 2. List any eight applications of DBMS. Ans: a) Banking b) Airlines c) Universities d) Credit card transactions e) Tele communication f) Finance g) Sales h) Manufacturing i) Human resources 3 Define instance and schema Ans: Instance: Collection of data stored in the data base at a particular moment is called an Instance of the database. Schema: The overall design of the data base is called the data base schema. 4 Define the terms 1) physical schema 2) logical schema. Ans: Physical schema: The physical schema describes the database design at the physical level, which is the lowest level of abstraction describing how the data are actually stored. Logical schema: The logical schema describes the database design at the logical level, which describes what data are stored in the database and what relationship exists among the data. 5 What is conceptual schema? Ans: The schemas at the view level are called subschemas that describe different views of the database. 6 What is storage manager? Ans: A storage manager is a program module that provides the interface between the low level data stored in a database and the application programs and queries submitted to

22 Module 1 : Introduction to Database Concepts 22 the system. 7 What are the components of storage manager? Ans: The storage manager components include a) Authorization and integrity manager b) Transaction manager c) File manager d) Buffer manager 1.9. Long Answer Questions: 1. Explain Disadvantages of file processing System. Ans: Database System Concepts- by Korth, Slberchatz,Sudarshan, 5th Edition,Chapter 1, Page 3 Module Explain the difference between logical and physical data independence. Ans: Database System Concepts- by Korth, Slberchatz,Sudarshan, 5th Edition,Chapter 1, Page 7 Module What are Advantages and Disadvantages of DBMS? Ans: The advantages and disadvantages of DBMS are as follows: Advantages: Reduced data redundancy Reduced updating errors and increased consistency Greater data integrity and independence from applications programs Improved data access to users through use of host and query languages Improved data security Reduced data entry, storage, and retrieval costs Facilitated development of new applications program Disadvantages: Database systems are complex, difficult, and time-consuming to design Substantial hardware and software start-up costs Damage to database affects virtually all applications programs Extensive conversion costs in moving form a file-based system to a database system Initial training required for all programmers and users. 4. Explain Overall architecture of DBMS with diagram. Ans: Database System Concepts- by Korth, Slberchatz,Sudarshan, 5th Edition,Chapter 1, Page 25 Module Explain Database applications. Ans: Database System Concepts- by Korth, Slberchatz,Sudarshan, 5th Edition,Chapter 1, Page 1 Module Explain Different Database Users. Ans: Database System Concepts- by Korth, Slberchatz,Sudarshan, 5th Edition,Chapter 1, Page 26 Module Explain Role and Responsibilities of DBA?

23 Module 1 : Introduction to Database Concepts 23 Ans: Database System Concepts- by Korth, Slberchatz,Sudarshan, 5th Edition,Chapter 1, Page 27 Module University Questions: 1. What is a database? Explain with examples. Also list the advantages of a database [Dec 15] system. 2. List four significant differences between file processing system and database [June 15] management system. 3. Explain Advantages of DBMS over file system [Dec 14] 4. Draw and explain Database system structure [June 15] 5. Define the Data Independence and explain its difference [Dec13,Dec 14] References: 1. G. K. Gupta : Database Management Systems, McGraw Hill. 2. Korth, Slberchatz,Sudarshan, : Database System Concepts, 6th Edition, McGraw Hill 3. Elmasri and Navathe, Fundamentals of Database Systems, 5thEdition, PEARSON Education. Practice for Module 1 1. List five responsibilities of a database management system. For each responsibility, explain the problems that would arise if the responsibility were not discharged. (10 M) 2. Design a database for Hospital Management system. (10 M) 3. List six major steps that you would take in setting up a database for a particular enterprise.(5 M) Self-assessment 1. Why would you choose a database system instead of simply storing data in operating system files? 2. When would it make sense not to use a database system? 3. What is logical data independence and why is it important? 4. Explain the difference between logical and physical data independence. 5. Explain the difference between external, internal, and conceptual schemas. How are these different schema layers related to the concepts of logical and physical data independence? 6. What are the responsibilities of a DBA? 7. Distinguish between logical and physical database design.

24 Module 1 : Introduction to Database Concepts Describe and define the key properties of a database system. Give an organizational example of the Name of Student Class Roll No. Subject Module No. S.No benefits of each property Self-evaluation 1. Do you understand the various types database users? Tick Your choice 2. Do you understand the Data Independence? o Yes 3. Do you know the difference between DBMS and File System? 4. Do you understand how database is helpful in real life applications? 5. Do you understand module? Yes, Completely. Partialy. No, Not at all. o o o o o o o Yes No No Yes No Yes No