Build a Junction Table for Many-to-Many Relationships

Designing a Junction Table for Many-to-Many Relationships

Write a SQL query to design a junction table for a many-to-many relationship.

Solution:

-- Tables representing entities in a many-to-many relationship.
CREATE TABLE Students (
    StudentID INT PRIMARY KEY,
    Name VARCHAR(100)
);

CREATE TABLE Courses (
    CourseID INT PRIMARY KEY,
    CourseName VARCHAR(100)
);

-- Junction table to resolve many-to-many relationship.
CREATE TABLE StudentCourses (
    StudentID INT,
    CourseID INT,
    PRIMARY KEY (StudentID, CourseID),
    FOREIGN KEY (StudentID) REFERENCES Students(StudentID),
    FOREIGN KEY (CourseID) REFERENCES Courses(CourseID)
);

Explanation:

• Purpose of the Query :
• The goal is to design a junction table to represent a many-to-many relationship between students and courses.
• Key Components :
  • StudentCourses: Links students to courses using foreign keys.
  • Composite primary key ensures unique combinations of student and course IDs.
• Why use Junction Tables? :
• Junction tables resolve many-to-many relationships by introducing an intermediary table.
• They simplify querying and maintaining relationships.
• Real-World Application :
• In enrollment systems, junction tables track which students are enrolled in which courses.

Notes:

• Junction tables often include additional attributes (e.g., enrollment date).
• Ensure proper indexing for efficient joins.
• Avoid redundant entries in the junction table.

For more Practice: Solve these Related Problems:

• Write a SQL query to design a junction table for a many-to-many relationship between books and authors.
• Write a SQL query to create a junction table for a many-to-many relationship between students and extracurricular activities.
• Write a SQL query to design a junction table for a many-to-many relationship between employees and projects.
• Write a SQL query to create a junction table for a many-to-many relationship between products and suppliers.

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