MYSQL Tutorial

🔗 Relational Databases in MySQL

MySQL is a relational database management system (RDBMS). This means it stores data in a structured format using **tables** and allows relationships between those tables using keys.

📊 Example Tables

Let's imagine a school database with two related tables:

🧑‍🎓 Students Table

📚 Marks Table

🔗 How Are They Related?

The student_id in the Marks table is a foreign key that links back to the Students table. This is how relationships are created.

🛠️ Creating Tables with Relationships

-- Create Students table
CREATE TABLE students (
  student_id INT PRIMARY KEY,
  name VARCHAR(50),
  class INT
);

-- Create Marks table with foreign key
CREATE TABLE marks (
  mark_id INT PRIMARY KEY,
  student_id INT,
  subject VARCHAR(50),
  score INT,
  FOREIGN KEY (student_id) REFERENCES students(student_id)
);
  

🔎 Fetching Related Data (JOIN)

-- Join both tables to see student names with marks
SELECT students.name, marks.subject, marks.score
FROM students
JOIN marks ON students.student_id = marks.student_id;
  

✅ Summary

• Relational databases store data in related tables.
• Primary key uniquely identifies each row in a table.
• Foreign key creates a link between two tables.
• We use JOIN to combine data from multiple tables.