An RDBMS (Relational Database Management System) is software used to create, manage, and interact with relational databases, where data is stored in tables (also called relations). These tables are made up of rows and columns, with relationships between them based on keys.
🔧 Key Concepts of RDBMS
| Term | Description |
|---|---|
| Table | A collection of rows and columns. Each table represents one entity (like Users). |
| Row (Record) | A single entry in a table, representing one instance of the entity. |
| Column (Field) | A specific attribute of the entity (like name, email, age). |
| Primary Key | A column (or group of columns) that uniquely identifies each row in a table. |
| Foreign Key | A column that links to the primary key of another table, creating relationships. |
| SQL | Structured Query Language — used to query and manipulate data in RDBMS. |
📌 Examples of RDBMSs
- MySQL
- PostgreSQL
- Oracle Database
- Microsoft SQL Server
- SQLite
⚙️ How It Works (High-Level)
Imagine a simple blog site:
- You have a
Userstable and aPoststable. - Each post is linked to a user using a foreign key (
user_id). - You can write SQL queries like:
SELECT * FROM Posts WHERE user_id = 5;This fetches all posts by the user with ID 5.
✅ Advantages of RDBMS
- Data Integrity via constraints (primary keys, foreign keys).
- Normalization: Avoids redundancy.
- ACID compliance: Ensures reliable transactions (Atomicity, Consistency, Isolation, Durability).
- Security: Access control through user roles and permissions.
❌ Limitations
- Less efficient for unstructured or semi-structured data (use NoSQL in such cases).
- Can become slow with very large or complex datasets if not indexed or normalized well.
- Horizontal scaling is harder compared to NoSQL systems.
🧠 Use Cases
- Banking systems
- E-commerce websites
- Enterprise resource planning (ERP)
- Customer relationship management (CRM)