SQL INNER JOIN

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INNER JOIN combines rows from two or more tables only when matching values exist in both.

🔹 Basic Syntax

SELECT columns
FROM table1
INNER JOIN table2
  ON table1.common_column = table2.common_column;

🔹 Example: Employees and Departments

SELECT
  e.employee_name,
  d.department_name
FROM employees e
INNER JOIN departments d
  ON e.department_id = d.department_id;

✅ This returns only those employees who are assigned to a department.

🔹 Join on Multiple Conditions

SELECT *
FROM orders o
INNER JOIN customers c
  ON o.customer_id = c.customer_id
  AND o.region = c.region;

🔹 Using Table Aliases (Best Practice)

Shortens query and improves readability:

SELECT e.name, d.name
FROM employees e
INNER JOIN departments d
  ON e.dept_id = d.id;

🧠 Quick Recap

🔗 Use INNER JOIN to extract meaningful data from related tables