SQL
The standard language for querying and modifying relational databases.
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Overview
SQL (Structured Query Language) is the standard language for defining, querying, and modifying data in relational databases -- tables of rows and columns connected by keys. Every major relational database (PostgreSQL, MySQL, SQL Server, SQLite) speaks a dialect of SQL, so the core skills transfer directly.
- What it is
- A declarative language for querying and modifying data stored in tables.
- Why it's used
- It's the near-universal interface to relational databases -- learning it once transfers across PostgreSQL, MySQL, SQL Server, and more.
- Where it fits
- Wherever an application stores structured, related data -- covered directly in this platform's Git, APIs & SQL course.
Core concepts
- Tables, rows, and columns
- SELECT, WHERE, ORDER BY
- JOINs across tables
- INSERT, UPDATE, DELETE
- GROUP BY and aggregation
Example
SQL is declarative: you describe what data you want (books under $15, most expensive first), and the database figures out how to retrieve it efficiently.
SELECT title, price
FROM books
WHERE price < 15
ORDER BY price DESC;Common use cases
- Any application storing structured, related data
- Data analysis and reporting
Project ideas
- Write queries against a small bookstore dataset: filtering, sorting, and joining authors to books