Post #1298

SQL Joins – Essential Concepts🚀 1️⃣ What Are SQL Joins? SQL Joins are used to combine rows from two or more tables based on a related column. 2️⃣ Types of Joins INNER JOIN: Returns only matching rows from both tables. SELECT * FROM TableA INNER JOIN TableB ON TableA.id = TableB.id; LEFT JOIN (LEFT OUTER JOIN): Returns all rows from the left table and matching rows from the right table. SELECT * FROM TableA LEFT JOIN TableB ON TableA.id = TableB.id; RIGHT JOIN (RIGHT OUTER JOIN): Returns all rows from the right table and matching rows from the left table. SELECT * FROM TableA RIGHT JOIN TableB ON TableA.id = TableB.id; FULL JOIN (FULL OUTER JOIN): Returns all rows when there is a match in either table. SELECT * FROM TableA FULL JOIN TableB ON TableA.id = TableB.id; 3️⃣ Self Join A table joins with itself to compare rows. SELECT A.name, B.name FROM Employees A JOIN Employees B ON A.manager_id = B.id; 4️⃣ Cross Join Returns the Cartesian product of both tables (every row from Table A pairs with every row from Table B). SELECT * FROM TableA CROSS JOIN TableB; 5️⃣ Joins with Multiple Conditions Using multiple columns for matching. SELECT * FROM TableA INNER JOIN TableB ON TableA.id = TableB.id AND TableA.type = TableB.type; 6️⃣ Using Aliases in Joins Shortens table names for better readability. SELECT A.name, B.salary FROM Employees A INNER JOIN Salaries B ON A.id = B.emp_id; 7️⃣ Handling NULLs in Joins Use COALESCE(column, default_value) to replace NULL values. IS NULL to filter unmatched rows in LEFT or RIGHT JOINs. Free SQL Resources: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v React with ❤️ for free resources Share with credits: https://t.me/sqlspecialist Hope it helps :)