Database & RDBMS Basics

1. Database & RDBMS Basics

What is a Database?

A database is an organized collection of structured data stored electronically. A DBMS (Database Management System) is software that manages this data.

RDBMS vs DBMS

Feature	DBMS	RDBMS
Data Storage	Files	Tables (rows + columns)
Relationships	Not enforced	Enforced via keys
ACID	Not always	Yes
Examples	File system, XML	MySQL, PostgreSQL, Oracle

Key Terminology

Term	Definition
Table	A collection of rows and columns (like a spreadsheet)
Row / Record	A single data entry in a table
Column / Field	A category of data (attribute)
Schema	The structure/blueprint of a database
Query	A request to retrieve or manipulate data
Relation	A table in relational model terms

SQL Sublanguages

DDL  (Data Definition Language)    → CREATE, ALTER, DROP, TRUNCATE
DML  (Data Manipulation Language)  → SELECT, INSERT, UPDATE, DELETE
DCL  (Data Control Language)       → GRANT, REVOKE
TCL  (Transaction Control Language)→ COMMIT, ROLLBACK, SAVEPOINT
DQL  (Data Query Language)         → SELECT