Database Design 101: Building a Library Management System from Scratch

Designing a database is one of the most important skills for any backend developer. A well-designed database improves performance, scalability, and data integrity—while a poor design creates bugs that are hard to fix later.

In this guide, we’ll design a real-world Library App database schema from scratch, focusing on practical structure, relationships, and SQL implementation, not just theory.

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What Is Database Design?

Database design is the process of organizing data into tables, defining relationships, and applying rules so data remains consistent, searchable, and scalable.

For a Library Management System, we need to manage:

• Books

• Authors

• Members

• Borrowing records

• Categories

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Step 1: Identify Core Entities (Library App)

Before writing SQL, we identify entities (tables).

Core Tables Needed

1. books

2. authors

3. book_authors

4. members

5. loans

6. categories

This approach avoids duplication and follows database normalization rules.

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Step 2: Database Schema Overview (High Level)

Table	Purpose
books	Stores book details
authors	Stores author information
book_authors	Handles many-to-many relationship
members	Library users
loans	Tracks borrowed books
categories	Book classification

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Step 3: Create the Library Database Schema (SQL)

Below is a real, production-ready SQL schema (MySQL / PostgreSQL compatible).

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1️⃣ Books Table

CREATE TABLE books 
(
    book_id INT PRIMARY KEY AUTO_INCREMENT,
    title VARCHAR(255) NOT NULL,
    isbn VARCHAR(20) UNIQUE,
    published_year INT,
    category_id INT,
    total_copies INT DEFAULT 1,
    available_copies INT DEFAULT 1,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

📌 Why this design?

• Avoids duplicate ISBNs

• Tracks total vs available copies

• Flexible for future expansion

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2️⃣ Authors Table

CREATE TABLE authors (
    author_id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(150) NOT NULL
);

Books can have multiple authors, so we separate this table.

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3️⃣ Book-Authors (Many-to-Many Relationship)

CREATE TABLE book_authors
 (
    book_id INT,
    author_id INT,
    PRIMARY KEY (book_id, author_id),
    FOREIGN KEY (book_id) REFERENCES books(book_id),
    FOREIGN KEY (author_id) REFERENCES authors(author_id)
);

This table connects books and authors without duplication.

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4️⃣ Categories Table

CREATE TABLE categories 
(
    category_id INT PRIMARY KEY AUTO_INCREMENT,
    category_name VARCHAR(100) UNIQUE NOT NULL
);

Categories make searching and filtering efficient.

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5️⃣ Members Table

CREATE TABLE members
 (
    member_id INT PRIMARY KEY AUTO_INCREMENT,
    full_name VARCHAR(150) NOT NULL,
    email VARCHAR(150) UNIQUE,
    join_date DATE DEFAULT CURRENT_DATE
);

Each member has a unique identity.

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6️⃣ Loans Table (Core Logic)

CREATE TABLE loans 
(
    loan_id INT PRIMARY KEY AUTO_INCREMENT,
    book_id INT,
    member_id INT,
    issue_date DATE DEFAULT CURRENT_DATE,
    return_date DATE,
    status ENUM('ISSUED', 'RETURNED') DEFAULT 'ISSUED',
    FOREIGN KEY (book_id) REFERENCES books(book_id),
    FOREIGN KEY (member_id) REFERENCES members(member_id)
);

This table controls who borrowed what and when.

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Step 4: Entity Relationships (Explained)

Relationship	Type
Books ↔ Authors	Many-to-Many
Books ↔ Categories	Many-to-One
Members ↔ Loans	One-to-Many
Books ↔ Loans	One-to-Many

This structure follows 3rd Normal Form (3NF).

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Step 5: Sample Queries (Real Usage)

Borrow a Book

INSERT INTO loans (book_id, member_id)
VALUES (1, 3);

UPDATE books
SET available_copies = available_copies - 1
WHERE book_id = 1;

Return a Book

UPDATE loans
SET return_date = CURRENT_DATE,
    status = 'RETURNED'
WHERE loan_id = 5;

UPDATE books
SET available_copies = available_copies + 1
WHERE book_id = 1;

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Step 6: Why This Database Design Works

✔ Avoids data redundancy
✔ Easy to scale
✔ Clean relationships
✔ Adheres to normalization
✔ Works for web & mobile apps