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DataBase Management Systems Notes
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Roll
Name
Age
1
ABC
19
2
DEF
22
3
XYZ
28
Roll Address
- KOL
- DEL
- MUM
UNIT-1
Introduction to Database Management System As the name suggests, the database management system consists of two parts. They are:
- Database and
- Management System
What is a Database?To find out what database is, we have to start from data, which is the basic building block of any DBMS.Data: Facts, figures, statistics etc. having no particular meaning (e.g. 1, ABC, 19 etc).Record: Collection of related data items, e.g. in the above example the three data items had no meaning. But if we organize them in the following way, then they collectively represent meaningful information.Roll Name Age
1 ABC 19
Table or Relation: Collection of related
records.
Roll Name Age
1 ABC 19
2 DEF 22
3 XYZ 28
The columns of this relation are called Fields, Attributes or Domains. The rows are called Tuples or Records.Database: Collection of related relations. Consider the following collection of tables: T1 T2 T3 T4
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Age and Hostel attributes are in different tables.A database in a DBMS could be viewed by lots of different people with different responsibilities.
Figure 1.1: Empolyees are accessing Data through DBMS
For example, within a company there are different departments, as well as customers, who each need to see different kinds of data. Each employee in the company will have different levels of access to the database with their own customized front-end application.
In a database, data is organized strictly in row and column format. The rows are called Tuple or Record. The data items within one row may belong to different data types. On the other hand, the columns are often called Domain or Attribute. All the data items within a single attribute are of the same data type.
What is Management System?
A database-management system (DBMS) is a collection of interrelated data and a set of programs to access those data. This is a collection of related data with an implicit meaning and hence is a database.The collection of data, usually referred to as the database, contains information relevant to an
Roll
Year
1
I
2
II
3
I
Year
Hostel I H1 II H2
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Page 4 enterprise. The primary goal of a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient. By data, we mean known facts that can be recorded and that have implicit meaning.
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. In addition, the database system must ensure the safety of the information stored, despite system crashes or attempts at unauthorized access. If data are to be shared among several users, the system must avoid possible anomalous results.
Database Management System (DBMS) and Its Applications:
A Database management system is a computerized record-keeping system. It is a repository or a container for collection of computerized data files. The overall purpose of DBMS is to allow he users to define, store, retrieve and update the information contained in the database on demand. Information can be anything that is of significance to an individual or organization.
Databases touch all aspects of our lives. Some of the major areas of application are as follows:
- Banking
- Airlines
- Universities
- Manufacturing and selling
- Human resources
Enterprise Information
◦ 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 inwarehouses 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.
◦ 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 and bonds; also for storing real-time market data to enable online trading by customers and automated trading by the firm.• 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.
Purpose of Database Systems
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