Database Management System

Study Notes

Data is the basic resource of an organization, and proper organization and management are required for the organization to run smoothly.
Accurate and reliable data is necessary for better decision making, ensuring privacy of data, and controlling data efficiently.

Data is known facts or figures that have implicit meaning.
Data can also be defined as the representation of facts, concepts, or instructions in a formal manner, suitable for understanding and processing.
Data can be represented in alphabets (A-Z, a-z), digits (0-9), and using special characters (+, -, #, $, etc.).

Information is processed data on which decisions and actions are based.
Information can be defined as organized and classified data to provide meaningful values.
Example: "The age of Ravi is 25" is information.

A file is a collection of related data stored in secondary memory.
In a file-oriented approach, each application has a separate master file and its own set of personal files.

Data redundancy and inconsistency: same information may be written in several files, leading to higher storage and access cost and data inconsistency.
Difficulty in accessing data: conventional file processing systems do not allow data to be retrieved in a convenient and efficient manner according to user choice.
Data isolation: data are scattered in various files, making it difficult to retrieve appropriate data with new application programs.
Integrity problems: enforcing data validation is difficult when new constraints are added.
Atomicity: ensuring atomicity is difficult in a file processing system when transaction failure occurs.
Concurrent access: it is not possible to access the same file for multiple transactions at the same time.
Security problems: there is no security provided in file processing systems to secure data from unauthorized user access.

A database is an organized collection of related data of an organization stored in a formatted way, shared by multiple users.
The main features of data in a database are:
- Well-organized
- Related
- Accessible in a logical order without any difficulty
- Stored only once
Example: a student file containing roll no, name, and address is a collection of related data with an implicit meaning.
Data in a database may be persistent, integrated, and shared.

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