? MySQL JOIN Multiple Tables

? Quick Overview

MySQL allows joining multiple tables using the JOIN keyword. This enables combining related data from several tables into a single result set using common columns.

? Key Concepts

INNER JOIN – Matches records in both tables
LEFT JOIN – All rows from left table + matching right rows
RIGHT JOIN – All rows from right table + matching left rows
CROSS JOIN – Cartesian product of tables

? Syntax / Theory

? View Code Example

// Syntax for joining multiple tables
SELECT column1, column2
FROM table1
JOIN table2 ON table1.column = table2.column
JOIN table3 ON table2.column = table3.column;

? Code Examples

? students Table

? View Code Example

// Sample data from students table
id | name
---------
1  | Alice
2  | Bob

? courses Table

? View Code Example

// Sample data from courses table
id | course
-----------
1  | Math
2  | Science

? enrollments Table

? View Code Example

// Mapping students to courses
student_id | course_id
----------------------
1          | 1
2          | 2

⚙️ Joining the Tables

? View Code Example

// Joining three tables using INNER JOIN
SELECT students.name, courses.course
FROM students
JOIN enrollments ON students.id = enrollments.student_id
JOIN courses ON enrollments.course_id = courses.id;

? Live Output / Explanation

? View Output

// Result after joining all tables
name  | course
--------------
Alice | Math
Bob   | Science

? Interactive Explanation

This query starts from students, matches records in enrollments, and finally links to courses, ensuring data consistency across all tables.

? Use Cases

Student-course management systems
Employee-department-project mapping
E-commerce orders with customers and products

? Tips & Best Practices

Always define accurate ON conditions
Prefer INNER JOIN for strict matching
Use LEFT JOIN when optional data is needed

? Try It Yourself

Practice combining INNER and LEFT JOINs
Create additional tables like teachers and departments
Experiment with multi-level JOIN conditions