Today, let's understand SQL JOINS in detail: 📝

SQL JOINs are used to combine rows from two or more tables based on related columns.

🟢 1. INNER JOIN
Returns only the matching rows from both tables.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
INNER JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: Employees with assigned departments only.

🔵 2. LEFT JOIN (LEFT OUTER JOIN)
Returns all rows from the left table, and matching rows from the right table. If no match, returns NULL.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
LEFT JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: All employees, even those without a department.

🟠 3. RIGHT JOIN (RIGHT OUTER JOIN)
Returns all rows from the right table, and matching rows from the left table. If no match, returns NULL.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
RIGHT JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: All departments, even those without employees.

🔴 4. FULL OUTER JOIN
Returns all rows from both tables. Non-matching rows show NULL.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
FULL OUTER JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: See all employees and departments, matched or not.

📝 Tips:
⦁ Always specify the join condition (ON)
⦁ Use table aliases to simplify long queries
⦁ NULLs can appear if there's no match in a join

📌 SQL Roadmap: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v/1506

💬 Double Tap ❤️ For More!