INTRODUCTION TO DATABASE MANAGEMENT SYSTEMS
Mohammed Sanaulla Khan
A collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes. The following are examples of database applications: ✓ computerized library systems
✓ automated teller machines
✓ flight reservation systems
✓ computerized parts inventory systems
From a technical standpoint, DBMSs can differ widely. The terms relational, network, flat, and hierarchical all refer to the way a DBMS organizes information internally. The internal organization can affect how quickly and flexibly you can extract information. Introduction
A database consists of four elements as given,
➢ Data are binary computer representations of stored logical entities. ➢ Software is divided into two general categories-data and programs. ➢ A program is a collection of instruction for manipulating data. ➢ Data exist is various forms- as numbers tents on pieces of paper, as bits and bytes stored in electronic memory or as facts stored in a persons mind. 2) Relationships
➢ Relationships explain the correspondence between various data elements.
➢ Are predicates that define correct database states.
➢ Schema describes the organization of data and relationships within the database. ➢ Schema defines various views of the database for the use of various system components of the database management system and for the application’s security. ➢ A schema separates physical aspects of data storage form the logical aspects of data representation. [pic]
Types of schema
➢ Internal schema: defines how and where the data are organized in physical data storage. ➢ Conceptual schema: defines the stored data structures in terms of the database model used. ➢ External schema: defines a view (or) views of the database for particular uses. ➢ In database management systems data files are the files that store the database information whereas offer files, such as index files and data dictionaries, store administrative information known as metadata. Data base are organized by fields, records and files.
i) Fields: is a single piece of information.
ii) Record: is one complete set of fields.
iii) File: is a collection of records.
Advantage of Data in database
Database system provides the organization with centralized control of its data Redundancy can be reduced:
In non-database systems, each application (or) department has its own private file resulting in considerable amount of redundancy (or) the stored data. Thus storage space is wasted. By having centralized database most of this can be avoided Inconsistency can be avoided:
When the same data is duplicated and changes are made at one site, which is not propagated to the other sites, it gives rise to inconsistency. If the redundancy is removed chances of having inconsistent data is removed. Data can be saved:
The existing application can save the data in a database.
Standards can be enforced:
With the central control of the database, the database administrator can Enforce standards. Integrity can be maintained
Integrity means that the data in the database is accurate. Centralized control of the date helps in permitting to define integrity constraints to the data in the database.
Characteristics of Data in a Database
The data in a database should have the following features:
1. Shared – Data in a database are shamed among different users and applications. 2. Persistence – Data in a database exist permanently in the sense the data can live beyond the scope of the process that created it. 3....
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