Table of Contents
What is a Relational Database Management System RDBMS?
A Relational Database Management System RDBMS is a fancy way of saying a database that is used to organize things in the form of tables. RDBMS is like having several spreadsheets that are linked to each other. They use primary keys and foreign keys to link them and distinguish one from the other. It is like a software companion that assists in managing these interactions to avoid the mess that would result from trying to sort through all that data. It is like a data coordinator that organizes your data and ensures that all your data is in the right place and all is well between the data.
Examples of Relational Database Management System (RDBMS):
- SQL Server
- Oracle
- MySQL
Basic Structure of Relational Databases
A database is a collection of data(tables). A table is a data structure that organizes data in rows(tuples) and columns(attributes).
Are tables only for storing data? No. Tables represent both data and relationships between data.
Example: Student Table
| Roll Number | Name |
|---|---|
| 101 | Muhammad Khan |
Here, the Roll Number (101) relates to Muhammad Khan, meaning there is a relationship between these values.
Tables also maintain relationships between different tables. For example, an advisor table can link a student table and an instructor table
Where is Relational Database Management System(RDBMS) Used?
- School Databases
- Banking Systems
- Hospital Information Management Systems
- Enterprise Database Management Systems
How does Relational Database Management System(RDBMS) work?
Multiple tables are used to store data and these tables are linked to each other by using keys such as Primary Key and Foreign Key. Now, let’s take an example of the Student and Department table.
Student Table:
| Student ID | Roll No | Name | Location | Photo | Department ID |
|---|---|---|---|---|---|
| 1 | 101 | Rahul | Pune |  | 201 |
| 2 | 102 | Nilesh | Mumbai | | 201 |
| 3 | 103 | Ketan | Nashik | | 202 |
| 4 | 104 | Nikhil | Pune | | 202 |
Department Table:
| Department ID | Department Name |
|---|---|
| 201 | Computer |
| 202 | IT |
In this example, Department ID is the Primary Key in the Department Table and acts as a Foreign Key in the Student Table, establishing a relationship between them.
Why is the Relational Model Popular?
- Easy to Understand: Data is stored in a tabular format using rows/tuples and columns/attributes.
- Reduces Redundancy: Using normalization, duplicate data is minimized/reduced.
- Efficient Data Operations: Supports CRUD operations – Create, Read, Update, Delete.
Database Operations in Relational Database Management System(RDBMS)
1. Insert Data
We can insert data into the database using DML (Data Manipulation Language).
Student Registration Form:
When the user clicks Save, the data gets stored in the database.
2. Update Data
If a student’s details need to be updated, we can use the UPDATE query by using DML Command.
- Change Location from Pune to Nashik
- Click Update
The database will now store the updated information.
3. Delete Data
If a student record needs to be deleted, we can use the DELETE query.
- Select Student ID
- Click Delete
The student’s record is permanently removed from the database by using the Delete command.
Normalization: Reducing Redundancy
Instead of repeating department names in multiple records, we create a separate Department table and refer to its ID in the Student Table. This:
- Saves database storage
- Removes redundancy
- Improves data integrity
Databases follow different models, including:
- Relational Model
- Entity-Relationship Model
- Object-Based Data Model
- Semi-Structured Data Model
Relational Model Terminology
In the relational model:
- Tables are called Relations
- Rows are called Tuples
- Columns are called Attributes
This terminology is due to the close connection between Relational Databases and Mathematics.
Instances and Schemas
- Instance: The data stored in a database at a given moment.
- Relation Instance: A specific set of rows within a relation.
Domain in Relational Databases
A domain is a set of permitted values.
Example: Banking Database
A bank has branches only in:
- New York
- Washington
- San Francisco
- Chicago
- Austin
If someone tries to insert “Los Angeles” as a branch, it will be invalid as it is not in the permitted domain.
Atomic Domains
A domain is atomic when its elements are indivisible.
Example: Phone Number
- If stored as a single value → Atomic
- If split into country code, area code, local number → Non-Atomic
Null Values in DBMS
A null value is not a blank space or zero. It represents unknown or non-existent data.
Example: Missing Phone Number
If a student has no phone number, the column should be null, not zero, as the number may be added later.
Sorted vs. Unsorted Relations
Relations are generally unsorted in storage. Sorting can be done during the display by using an order clause.
Example: Instructor Relation
| Instructor ID | Name | Department | Salary |
| 34586 | John | Biology | 65,000 |
Example: Student Relation
| Student ID | Name | Department | Credits |
| 103 | B | CS | 20 |
Example: Advisor Relation
| Student ID | Instructor ID |
| 103 | 25252 |
Here, Student ID 103 (B) is advised by Instructor ID 25252 (Alia).
Here is the difference between DBMS and RDBMS in a tabular format:
| Feature | DBMS (Database Management System) | RDBMS (Relational Database Management System) |
|---|---|---|
| Definition | A database management system (DBMS) manages data in a file system. | A relational database management system (RDBMS) manages data in a tabular format. |
| Storage Format | Data is stored in file systems. | Data is stored in a tabular format (rows and columns). |
| Data Representation | Data is represented in a hierarchical or navigational format. | Data is represented in tables. |
| Relationships | No relationship between one data and another data. | Relationships between data are represented in tables. |
| Normalization | Does not support normalization. | Supports normalization to reduce redundancy and optimize tables. |
| Distributed Databases | Does not support distributed databases. | Supports distributed databases. |
| Data Handling | Can handle a small amount of data. | Can handle a large amount of data, including complex data. |
| User Support | Supports only a single user. | Supports multiple users at a time. |
| Examples | Normal file system, XML, etc. | Oracle, SQL, MySQL, SQL Server, etc. |
This table presents a clear and structured comparison between DBMS and RDBMS
Homework
Try to identify the relationship between Student Relations, Instructor Relations, and Course Relations using the table below.
Example: Course Relation
| Course ID | Title | Department | Credits |
| CS101 | Intro to CS | CS | 3 |
| BIO105 | Fundamentals of Biology | Biology | 4 |
How do students and instructors relate to courses?
Understanding these relationships will help grasp the Relational Database Model better.
Conclusion
In this session, we covered the basics of RDBMS, including its format, most important features, and benefits. We learned how tables are connected through primary and foreign keys, so data is better managed and organized. We also studied real-life examples, like Student & Department tables, and realized why the relational model is preferred by everyone. In addition, we discussed critical database operations such as Insert, Update, and Delete, as well as why normalization is important in minimizing redundancy and enhancing data integrity. Grasping these principles is vital in managing relational databases for real-world applications. We learned the difference between the DBMS and RDBMS.