SQL Learning Hub
Learning Path
- SQL Basics
- Advanced Queries
- Joins & Relations
- Functions & Aggregation
- Practice Quiz
SQL Basics
SQL (Structured Query Language) is a standard programming language for managing and manipulating relational databases. Let's start with the basics:
Key Concepts
- Database: A collection of related data organized in tables
- Table: Data structured in rows and columns
- Query: A request for data or information from a database
- RDBMS: Relational Database Management System (MySQL, PostgreSQL, SQL Server, Oracle)
Basic SQL Commands
SELECT - extracts data from a database
UPDATE - updates data in a database
DELETE - deletes data from a database
INSERT INTO - inserts new data into a database
CREATE DATABASE - creates a new database
CREATE TABLE - creates a new table
DROP TABLE - deletes a table
ALTER TABLE - modifies a table
Your First SQL Query
The most common operation in SQL is retrieving data using the SELECT statement:
This query retrieves all columns (*) from the "customers" table where the country is "USA", and orders the results by the "last_name" column.
Try It Yourself
Write a query to select all products with a price greater than $50, ordered by price in descending order.