A database is an organised collection of data. It helps us to enter a large amount of data as well as to access , manage and analyse the data very quickly and effeciently.
In our daily life unknowingly we all use database as telephone diary, dictionary, maintaing a list of students and their addresses, keeping the records of students pertaining to their academic and co-curricular achievements, list of customers in a bank etc.
It is very difficult to maintain a database manually when it has hundreds or thousands of records. A DBMS (Database Management System) is a computerised record keeping system that enables us to create, store, modify and access information from a database.
Types of Database:
There are mainly two types of database.
Flat File Database:
A flat file database is the data file that contain records, has a small and fixed number of fields, without any structured relationship with other data files. For ex. MS Excel.
Relational Database:
A relational database is a type of database that stores data in different tables. These tables are related to each other in such a way that whenever there is a need, the data can be joined and information can be accessed from them at once. The relationship between different tables can be defined by their common fields.
The main property of a relational database lies in its capability to pull data from different but related tables conveniently and to join information from these tables to produce meaningful answers. For Ex. Oracle, Microsoft Access, Microsoft SQL Server, My SQL, IBM DB2 etc.
RDBMS
RDBMS stands for Relational Database Management System. It is a DBMS software which uses relational model for its database. In this model all the data is stored in a structured tabular format consisting of rows and columns. It also provides a facility to define a primary key for unique identification of each table. It provides the feature to create, update and administer a relational database. This makes it easy to search retrieve data within the database and ensures that data integrity is maintained. The relational structure makes it possible to run queries across multiple tables at once. An RDBMS may also provide a visual representation of the data. For example it may display data in table like a spreadsheet, allowing us to view and even edit individual values in the table.
DATABASE SERVERS:
A database server refers to a server which offers database services to other computer or computer programs which is known as the client-server model. Database servers are dedicated computers that hold the actual databases and run only the DBMS and related software. Users access a database server either through a "front-end" or a "back-end". In "front-end" it displays the requested data only and in 'back-end" it runs on the server and handles tasks such as data analysis and storage. Such type of data access is referred to as a client-server model.
DATABASE CONCEPTS:
A databse is the base for collection of data. The data in a database is organised in such a way that information within the databse can be easily retrieved and modified. The database is a repository of information needed for running certain functions in a corporation or organisation. The data should be accurate, private and protected from damage.
a) Data item: A database primarily contains information about a data item, for example a school database would contain information about students. Here the student is the data item and the details of the students like their address, ph nos, academic achievements are stored in database.
b) Fields: A field describe a particular attribute of the data item. For example, the field Roll No in student table will store the roll numbers of all the students.
c) Records: A record is a set of information(made up of fields) that belong to a data item. For example, when we enter data for all the fields, such as Roll No, Name, Marks etc, for a student, it creates a new record.
d) Value or Data: A value is a set of characters, text or numerical that you put in while adding information to your database. For example, 3, Dipti, 90, 88, 70 are the data values for the specific fields of the table, "students".
e) Table: When you put all the information like fields, records and values together in a grid, it forms a table. A table is a collection of similarv records in a database. A table stores data in form of rows and columns.
f) Database: A database can have one or many tables. It is basically a container that holds tables and other objects and manages how they can be used. When creating a database, an important feature is record uniqueness in every table. It is an important aspect to be able to distinguish between different items having duplicate values.
Uniqueness avoids the accidental duplication of records caused by a user or computer error. By having a unique value associated with each record, individual records can be selected, updated or deleted. In a database, one of the field can be identified as a key field to uniquely identify the record. Sometimes the data may not have this kind of a natural key. In this caase a surrogate key is used, i.e. a column will be added to a table whose purpose is to serve as a primary key. This ensures that every record in a table is a unique instance.
|
F_Name |
English |
Maths |
Hindi |
|
Sandeep |
89 |
79 |
60 |
|
Nitin |
65 |
80 |
77 |
|
Dipti |
90 |
88 |
70 |
|
Roll No |
F_Name |
English |
Maths |
Hindi |
|
1 |
Sandeep |
89 |
79 |
60 |
|
2 |
Nitin |
65 |
80 |
77 |
|
3 |
Dipti |
90 |
88 |
70 |
