Introduction: What is database management system
In this article we will cover what is a database or what is a database management system. A database is a collection of respective items group together under a single heading.
According to Oxford dictionary “a database is a organize store of data for computer processing.”
A DATABASE can be said as collection of files containing records of similar nature.
Each record contains all the data relating to one subject in the file. The grouping of such files is database .
Database Management system (DBMS): A database management system is a software which is use to manage all data from a database.
There are many database management system software are available in market.
Like : Mysql database management system, Oracle database management system etc.
Purpose of database
In the present day environment and due to computerization in various institutions and organizations.
The difficult activities are being perform on computers in the form of database and other data.
Manual process has been convert into computerize one and need of database is on increase.
The database are being manage due to one reason or other which have been explain below.
Data Redundancy Reduces: Database reduce redundancy to a maximum limit. Data redundancy is a sort of duplication data. In manual system, the work is done.
For example, In a school, manual database may be there. A student address may be record in fees section.
Library and administration section does not inform the fees section or library his old address is continue to be record in fees section and library.
If computerize database is maintain , the change in all files is record automatically.
Sharing of Data Possible: Database can be share when the data is centralize. If LAN system has been install in the institution.
Data can be share by different employees and workers by using their own password.
A lot of time is save in going here and there to collect data.
Easy Storage: The database is computerize environment can be store on hard disk or floppies .
It is very easy to take backup of database. It is possible by learning few commands.
Moreover, the data is in compress form and manual file work is not be done.
Computerized database saves lot of storage space.
Operations on Database
Various types of operations can done on database which are mention below:
Insert Data: The data can be insert into the database by creating a table or multiple tables.
Reproduction of Information: The store data can be produce as output.
Modification: The data inserted into the database can be modify according to needs.
Editing: The existing information in the database can be edit to rectify the error or for other purpose.
Deletion: The unnecessary data in the database can be delete.
Sequence: The data in the database can be arrange in sequence either in ascending order and in descending order or any other criteria.
Record: A record is a row of data in a database table consisting of a single value from each column of data in the table.The data in the columns in a table are all of the same type of data.Whereas the rows represent a given event.
Field: A field or combination of fields that uniquely identifies each record in a table.So that each record can be uniquely special from every other occurring in the table.
Data Entities: An entity is an object person or any event that the system stores information about.
It can have multiple event. Each entity has certain properties associated with it and operations applicable to it. Any entity is represent by rectangle in E-R model.
Attributes: A entity is represent by a set of attributes. Attribute is descriptive properties process by each member of an entity set.
Attribute are data elements that describe an entity. For each attribute, there is a set of permit values.
The destination of an attribute for an entity set describe that the database stores similar information concerning each entity of the entity set. Attribute can also describe properties of relations.
The value of attributes and values of an entity must be such that they can uniquely identify the entity.
No two entities is a entity set allow to exactly the same value of all attributes.
A key allow us to identify a set of attributes that distinguish entities from each other.Keys also help uniquely identify relationship and thus distinguish relationship from each other.
A key is a field or combination of fields , that uniquely identifies a record in a table.
Candidate key: One or more fields that will be identify one record in a table. A potential primary key.
Composite key: A key made up of two or more table columns that together guarantee uniqueness.When there is no single column available that can guarantee uniqueness by itself.
Foreign key: A column or group of columns in a table which corresponds to references a primary key in another table in a database.
A foreign key need to itself be unique but must uniquely identify the field or fields in a table that the key references.
Secondary key: A key that is not the primary key for a table.
Types of Database
Single file database: Single file database is “flat file” system. This type of database may contains several records with a fixed number of fields Since there is only one table in database however this database is without any structure relationship.
Multi-file Relational Database: Relational database are frequently “structure” database.
A relational database is a type of database which contains several tables.
The tables are respective to each other in such way that information can obtain from join tables.
Oracle, Base and MS Access are relational database programs.
Database Administrator (DBA) & DBMS
A database adminstrator (DBA) is a person who directs all activities related to maintaining a database .
The DBA has to perform duties of designing, implementing and maintaining the database system.
The DBA grants and revokes permissions for accessing database by the user. In the case of small institutions the role of DBA is perform by a single person.But the database of big corporations is manage by group of administrators.