Post #2396

🧠SQL Basics Cheatsheet📊🛠️ 1. What is SQL? SQL (Structured Query Language) is used to store, retrieve, update, and delete data in relational databases. 2. Common SQL Commands: - SELECT – Retrieves data - INSERT INTO – Adds new data - UPDATE – Modifies existing data - DELETE – Removes data - WHERE – Filters records - ORDER BY – Sorts results - GROUP BY – Aggregates data - JOIN – Combines data from multiple tables 3. Data Types (Examples): - INT, FLOAT, VARCHAR(n), DATE, BOOLEAN 4. Clauses to Know: - WHERE – Filters rows - LIKE, BETWEEN, IN, IS NULL – Conditional filters - DISTINCT – Removes duplicates - LIMIT – Restricts row count - AS – Rename columns 5. SQL JOINS (Very Important): - INNER JOIN – Matching rows in both tables - LEFT JOIN – All from left + matches from right - RIGHT JOIN – All from right + matches from left - FULL OUTER JOIN – All rows from both tables 6. Aggregate Functions: - COUNT(), SUM(), AVG(), MIN(), MAX() 7. Example Query: SELECT name, AVG(score) FROM students WHERE grade = 'A' GROUP BY name ORDER BY AVG(score) DESC; 8. Constraints: - PRIMARY KEY, FOREIGN KEY, NOT NULL, UNIQUE, CHECK 9. Indexing & Optimization: - Use INDEX to speed up queries - Avoid SELECT * in production - Use EXPLAIN to analyze query plans 10. Popular SQL Databases: - MySQL, PostgreSQL, SQLite, Microsoft SQL Server, Oracle Double Tap ♥️ For More