Ch 8: Introduction to DBMS
Data and Information
Data: raw facts about a person, place, activity or thing. Information: the processed or organised form of data (e.g. marks are data, a report card is information).
Database: a collection of logically related data stored in an organised manner. DBMS: software to create, update and retrieve data (e.g. MS Access, LibreOffice Base, Oracle, MySQL).
Advantages of DBMS
- Organised storage → fast, accurate retrieval.
- Minimal data redundancy and data consistency.
- Data sharing and increased security (passwords, encryption).
Data Models
| Model | Structure |
|---|---|
| Hierarchical | Tree-like (parent–child). |
| Network | Records linked to the same master (inverted tree). |
| Relational | Tables related by common fields — most common. |
Relational model was proposed by E. F. Codd in 1970.
RDBMS Terminology
| Term | Meaning |
|---|---|
| Entity | A real-world object (e.g. Student). |
| Field / Column | Smallest entity; holds one type of data. |
| Record / Row | Values for all fields of one object. |
| Primary Key | Uniquely identifies a row; no duplicate, no blank. |
| Foreign Key | Links to the primary key of another table. |
| Candidate / Alternate Key | Eligible keys; those not chosen are alternate keys. |
Primary vs Foreign key: Primary key uniquely identifies each record in its OWN table; foreign key matches the primary key of ANOTHER table and relates the two.
Summary
- Data = raw facts; Information = processed data.
- Models: Hierarchical, Network, Relational (Codd, 1970).
- Primary key = unique + not blank; foreign key relates two tables.
Data और Information
Data: किसी व्यक्ति, स्थान, गतिविधि या वस्तु के raw facts। Information: data का processed/organised रूप (marks = data, report card = information)।
Database: logically related data का organised collection। DBMS: data create, update, retrieve करने का software (MS Access, LibreOffice Base, Oracle, MySQL)।
DBMS के फ़ायदे
- Organised storage → तेज़, सटीक retrieval।
- कम data redundancy और data consistency।
- Data sharing और बढ़ी हुई security (passwords, encryption)।
Data Models
| Model | Structure |
|---|---|
| Hierarchical | Tree जैसा (parent–child)। |
| Network | Records एक master से जुड़े (inverted tree)। |
| Relational | Tables common fields से जुड़ी — सबसे आम। |
Relational model E. F. Codd ने 1970 में दिया।
RDBMS शब्दावली
| Term | अर्थ |
|---|---|
| Entity | वास्तविक वस्तु (जैसे Student)। |
| Field / Column | सबसे छोटी entity; एक प्रकार का data। |
| Record / Row | एक object के सभी fields के values। |
| Primary Key | row की unique पहचान; न duplicate, न blank। |
| Foreign Key | दूसरी table की primary key से जुड़ता है। |
| Candidate / Alternate Key | योग्य keys; जो न चुनी जाएं वे alternate keys। |
Primary vs Foreign key: Primary key अपनी table में हर record की unique पहचान है; foreign key दूसरी table की primary key से मेल खाकर दोनों को जोड़ता है।
सारांश
- Data = raw facts; Information = processed data।
- Models: Hierarchical, Network, Relational (Codd, 1970)।
- Primary key = unique + not blank; foreign key दो tables जोड़ता है।
Frequently Asked Questions
What is the difference between data and information?
Data is raw facts; information is the processed or organised form of data.
Who proposed the relational database model?
The relational model was proposed by E. F. Codd in 1970.
What is a primary key?
A primary key uniquely identifies each record in a table, with no duplicate and no blank values.