Relational Database Management System

What is RDBMS (Relational Database Management System)?

An RDBMS is a database software created to efficiently manage, store, and retrieve data organized in tables. These databases are fundamental to data-driven applications everywhere, from enterprise systems to mobile apps.

Core Features of RDBMS

• Tables:
  Data in an RDBMS is stored in tables, made up of rows and columns.

• Relationship:
  Tables can be linked together using keys, making data connected and easier to retrieve.

• SQL (Structured Query Language):
  Most RDBMS software uses SQL to query and manage data.

• ACID Properties:
  All major RDBMS platforms follow ACID rules—Atomicity, Consistency, Isolation, and Durability—to ensure reliable transactions.

• Popular Examples:

  • PostgreSQL
  • MySQL
  • Microsoft SQL Server
  • Oracle

Essential Components of Tables

• Rows (Records):
  The horizontal elements in a table; each row is a single data entry.

• Columns (Attributes):
  Vertical elements, representing data categories (e.g., Name, Age, Gender).

• Cardinality:
  Total number of rows in a table.

• Degree:
  Total number of columns in a table.

Table Constraints

Constraints are rules that ensure data accuracy and integrity in your tables. Common examples:

• Unique Constraint:
  Ensures all values in a column are different.

• Not Null Constraint:
  Ensures a column cannot have a null (empty) value.

• Default Constraint:
  Sets a default value for a column if none is provided.

Keys in RDBMS

Keys are crucial for uniquely identifying and relating data across tables. The main types include:

• Primary Key (PK):
  Uniquely identifies each record; cannot be null.

• Foreign Key (FK):
  Links to the Primary Key in another table, enabling relationships between tables.

• Composite Key:
  Made of two or more columns combined to uniquely identify a record.

• Unique Key:
  Ensures all values in a column are unique; unlike PK, can contain one null value.

In summary:
RDBMS software provides the foundation for secure, reliable, and organized data storage—making it essential for most modern applications. Whether you’re storing customer details or tracking inventory, understanding these core concepts will help you make the most of your database!