What is SQL?
Understanding SQL and relational databases
SQL (Structured Query Language) is the standard language for managing and manipulating relational databases. It's been around since the 1970s and remains the most important skill for working with data.
Why Learn SQL?
Universal Language
Works with PostgreSQL, MySQL, SQLite, SQL Server, and more
High Demand
Essential for developers, analysts, and data scientists
Declarative
Tell the database what you want, not how to get it
Powerful
Complex data transformations in a few lines
Relational Database Basics
Data is organized into tables (like spreadsheets) with rows (records) and columns (fields).
Example: users table
| id | name | created_at | |
|---|---|---|---|
| 1 | Alice Smith | alice@email.com | 2024-01-15 |
| 2 | Bob Johnson | bob@email.com | 2024-02-20 |
| 3 | Carol White | carol@email.com | 2024-03-10 |
SQL Command Categories
| Category | Commands | Purpose |
|---|---|---|
| DQL | SELECT | Query data |
| DML | INSERT, UPDATE, DELETE | Modify data |
| DDL | CREATE, ALTER, DROP | Define structure |
| DCL | GRANT, REVOKE | Control access |
Getting Started: This tutorial focuses on SELECT (reading data) as it's the most commonly used. You'll use it 90% of the time!