1.1. Introduction to Database
A database is a collection of inter–related data items that can be processed by one or more application systems. Data is a collection of raw information and information is a collection of processed data. A database also represents some aspects of the real world, sometimes called the mini-world or the Universe of Discourse (UOD).
- Banking: all transactions
- Airlines: reservations, schedules
- Universities: registration, grades
- Sales: Customers, products, purchases
- Manufacturing: production, inventory, orders
o Database has an availability of a storage system, the most obvious of these being persistence. We need persistent storage and storage must be reliable.
o Several users and/or several tools must be able to safely access the same data concurrently by using the database.
o We need a database, to share data of all kinds between users (except for very small systems), between tools working on them, and usually between different computers. All should be able to work with the same set of data.
o Database also needed to build computerized business applications, to create business applications that operate in multiple locations, to conduct business on the internet and also to enable customers to place orders using the web.
Database Management System (DBMS)
It is software that defines a database, stores the data, supports a query language, produces reports, and creates data entry screens. In other words, it is a collection of programs that enables us to store, modify, and extract information from a database. Example: FoxPro
Relational Database Management System (RDBMS)
RDBMS stands for Relational Database Management System. RDBMS stores the data into collection of tables, which might be related by common field of database table columns. RDBMS also provide relational operators to manipulate the data stored into the database tables. Example: Oracle, SQL Server etc
1.2. Advantages of DBMS
The DBMS (Database Management System) is preferred ever for the conventional file processing system due to the following advantages:
o Minimal data Redundancy
o Data consistency
o Integration of data
o Sharing of data
o Enforcement of standards
o Ease of application development Uniform security ,privacy and integrity
o Data independence
Minimal data Redundancy
o Redundancy means repetition or duplication of data.
o In DBMS, the data redundancy can be controlled or reduced but it is not removed completely. Sometimes, it is necessary to create duplicate copies of the same data items in order to relate tables with each other.
- By controlling the data redundancy, you can save storage space. Similarly, it is useful for retrieving data from database using queries.
Data consistency
- The DBMS also has system to maintain data consistency with minimal effort.
o Most systems enable us to create basic business rules when define the data.
Example: Price field should always be greater than zero.
These rules are enforced for every form, user or programs that access the data
Integration of data
o This is very easy in DBMS by using query language.
o If programmers create a separate programs and independent files to store the data, combining the data would be difficult.
- Since data in database is stored in tables, any data in the database can be easily retrieved combined and compared using the query system.
Sharing of data
In DBMS, data can be shared by authorized users of the organization. The DBA manages the data and gives rights to users to access the data. Many users can be authorized to access the same set of information simultaneously.
Ease of application development
The cost and time for developing new applications is also reduced. The DBMS provides tools that can be used to develop application programs. For example, some wizards are available to generate Forms and Reports. Stored procedures (stored on server side) also reduce the size of application programs.
Uniform security, privacy and integrity
Centralized control and standard procedures can improve data protection in DBMS. The uniform Security, privacy and integrity should be easily provided by DBMS.
Example: The value of the sex field should be among the values (male, female), Average marks should fall between 0 to 100 etc.
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