SQL Basics

SQL (Structured Query Language) is the standard language used to communicate with relational databases - to create structures, insert and modify data, and retrieve exactly the information you need.

Categories of SQL Commands

• DDL (Data Definition Language) - CREATE, ALTER, DROP - defines database structure
• DML (Data Manipulation Language) - INSERT, UPDATE, DELETE - manipulates data
• DQL (Data Query Language) - SELECT - retrieves data
• DCL (Data Control Language) - GRANT, REVOKE - manages permissions

A First Query

SELECT first_name, city
FROM customers
WHERE city = 'Noida';

Why SQL Matters for Data Science

Most real-world data still lives in relational databases. Before any analysis or model building can begin, data scientists routinely use SQL to pull, filter, and join the exact data they need directly from the source.