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What is Database?
A database is a collection of information that is organized so that it can easily be accessed, managed and updated.
What is Database Management System?
DBMS is a software package designed to define, manipulate, retrieve and manage data in a database. It defines rules for validating and manipulating that data. Fourth generation query languages like SQL are used along with DBMS package to interact with database.
Some of the real time applications using DBMS are Banking (transactions), Airlines (reservations and schedules), Universities (registration and grades), Manufacturing (production, inventory, orders, supply chain) etc.
Advantages of a DBMS
Components of DBMS
A database system consists of 4 components usually:
1. Data: It is the most important component of a database which acts like a bridge between hardware and software. Different types of data are- User data (actual/workable data stored in tables), Metadata ( data about data i.e no of tables, no of fields), application metadata (structure and format of queries)
2. Hardware: Storage devices on which data is stored with i/o operations (hard disks, optical disks, magnetic tapes etc)
3. Software: It acts a bridge between user and database. It interacts with both user and database and acts a medium for data exchange. For performing various operations on the data, we use query languages like SQL etc.
4. Users: They are the ones who need information from a database to carry out their primary business responsibilities. Various types of users are: Database administrators, Database designers, End users, Application Programmers.
Levels of Abstraction
1. Physical Level
It describes how a record (e.g. customer) is stored in the database.
2. Logical Level
It describes the data stored in database and the relationships among themselves. Lets look at the description of customer data below:
cust city: string;
3. View Level
At this level, application programs hide details of data types. Views can also hide information such as employee salary for security purposes.