CBSE Class 12 Computer Science Database Concepts And Sql Worksheet

Database is a collection of different kinds of data which are connecting with some relation.

In different way, it is a computer based record keeping system. The collection of data referred to as a database.

Purpose of Database :

Years ago, for keeping record, a typical file-processing system is used. A number of different application programs are written to extract records from and add records to the appropriate files. But this scheme has a number of major limitations and disadvantages, such as data redundancy, data inconsistency, unsharable data, unstandardized data, insecure data, incorrect data, etc.

A database management system is answer to all these problems as it provides a centralized control of the data.

1. Databases reduce the data redundancy to a large extent

2. Databases can control data inconsistency to a large extent

3. Databases facilitate sharing of data

4. Databases enforce standards

5. Databases can ensure data security

6. Integrity can be maintained through databases

Data : It is row facts, figures, characters, etc with which we have to start.

Information : The processed data or meaningful data is known as information.

Database : An organized collection of relational data is called as database.

DBMS : It is a Database Management System. It is a system to used for create database, store the data, secure it and fetch data whenever required. MS Access, Oracle is the example of DBMS. Database Abstraction :

A major purpose of a database system is to provide the users only that much information that is required by them. This means that the system does not disclose all the details of data, rather it hides certain details of how the data is stored and maintained. A good database system ensures easy, smooth and efficient data structures in such a way so that every type of database user : end user, application system analyst, and physical storage system analyst, is able to access its desired information efficiently. Various Levels of Database Implementation :

1. Internal Level (Physical Level) : This level describes how the data are actually stored on the storage medium. At this level, complex low-level data structures are described in details. Eg. RollNo is in Byte(4), offset = 34.

2. Conceptual Level : It describes what data are actually stored in the database. It also describes the relationships existing among data. Eg. ItemCode is in Numeric(5).

3. External Level (View Level – Logical Level) : This is the level closest to the users. It is concerned with the way in which the data are viewed by individual users. Most of the users of the database are not concerned with all the information contained in the database. Eg. View 1 contains RollNo, Name, DOB