MENU
SQL - RDBMS Overview
A Relational Database Management System (RDBMS) is a software system designed to store, manage, and retrieve structured data efficiently. It organizes data into tables consisting of rows and columns, linked by relationships. RDBMS ensures data integrity, security, and efficient querying using Structured Query Language (SQL).
Key Features of RDBMS
- Tabular Structure: Data is stored in tables with rows and columns.
- Primary & Foreign: Keys – Ensures unique identification and relationships between tables.
- ACID Compliance: Guarantees Atomicity, Consistency, Isolation, and Durability for reliable transactions.
- Data Integrity: Enforces constraints (e.g., NOT NULL, UNIQUE, CHECK).
- Scalability: Supports large datasets with indexing and partitioning.
- Multi-user Access: Allows concurrent access with locking mechanisms.
Popular RDBMS Examples
- MySQL: Open-source RDBMS used in web applications (e.g., WordPress, Facebook).
- PostgreSQL: Advanced open-source RDBMS with JSON support.
- Oracle Database: Enterprise-grade RDBMS for large-scale applications.
- Microsoft SQL Server: Windows-based RDBMS with business intelligence tools.
- SQLite: Lightweight, file-based RDBMS for mobile apps (e.g., Android, iOS).
Example: Student Database in RDBMS
Consider a university database with some tables:
Student Table
| ID | Name | Age | Address | Phone | Department ID | ||
|---|---|---|---|---|---|---|---|
| 1 | Alice Johnson | 21 | New York | alice@example.com | 1234567890 | 1 | |
| 2 | Bob Smith | 22 | Los Angeles | bob@example.com | 2345678901 | 2 | |
| 3 | Charlie Brown | 20 | Chicago | charlie@example.com | 3456789012 | 1 |
Department Table
| ID | Department Name |
|---|---|
| 1 | Computer Science |
| 2 | Information Tech |
Courses Table
| ID | Course Name | Description | Duration |
|---|---|---|---|
| 1 | SQL | SQL for beginners | 3 months |
| 2 | Python | Python programming | 4 months |
| 3 | Java | Java basics | 3 months |
In this schema, the ID column in each table serves as the primary key. The department_id in the student table, as well as the student_id and course_id in the student_courses table, are foreign keys. These foreign keys establish relationships between the tables.
Student Courses Table
| Student ID | Course ID |
|---|---|
| 1 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 1 |
Example: SQL Query to Find Students Who Took the SQL Course
SELECT Students.Name, Courses.CourseName FROM Students JOIN Courses ON Students.StudentID = Courses.StudentID WHERE Courses.CourseName = 'Database Systems';
Output
| Student ID | Name | Phone | Department | Course | |
|---|---|---|---|---|---|
| 1 | Alice Johnson | alice@example.com | 1234567890 | Computer Science | SQL |
| 3 | Charlie Brown | charlie@example.com | 3456789012 | Computer Science | SQL |
Advantages of RDBMS
- Data Consistency – Avoids redundancy using normalization.
- Flexible Querying – SQL allows complex data retrieval.
- Security – User authentication & role-based access.
- Backup & Recovery – Prevents data loss.
RDBMS is the backbone of modern data storage, used in banking, e-commerce, healthcare, and more. Learning RDBMS fundamentals (tables, keys, SQL) is essential for database administrators, developers, and data analysts.
153