BitWithBiteSQL · Quick Reference
Lesson 1 — Introduction to SQL & Databases Cheat Sheet
In one line: A database is an organized collection of structured data stored electronically. Unlike a spreadsheet, a database can store millions of rows efficiently and let multiple users qu...
Key Ideas
1What is a Database?. A database is an organized collection of structured data stored electronically. Unlike a spreadsheet, a database can store millions of rows efficiently and let multipl...
2Relational vs NoSQL. Relational: structured tables, ACID transactions, SQL language — MySQL, PostgreSQL, SQLite, SQL Server
3SQL Execution Order. SQL clauses execute in a different order than how you write them. Understanding this prevents confusing errors.
4Your First SQL Statement
SQL
-- The most basic SQL query
SELECT * FROM students;
-- Read it as: "Get all columns FROM the students table"
-- SELECT = what columns to return (* = all)
-- FROM = which table to look in
-- More specific:
SELECT name, age FROM students WHERE grade = 'A';
-- "Get name and age FROM students WHERE grade equals A"
Section 5
SQL Sublanguages. SQL is divided into four sublanguages, each serving a different purpose.
Code Examples
-- The most basic SQL query
SELECT * FROM students;
-- Read it as: "Get all columns FROM the students table"
-- SELECT = what columns to return (* = all)
-- FROM = which table to look in
-- More specific:
SELECT name, age FROM students WHERE grade...