Library-Management-System-using-SQL

##Project Overview-
This project demonstrates the implementation of a Library Management System using SQL. It includes creating and managing tables, performing CRUD operations, and executing advanced SQL queries. The goal is to showcase skills in database design, manipulation, and querying.

##Objectives-
Set up the Library Management System Database: Create and populate the database with tables for branches, employees, members, books, issued status, and return status. CRUD Operations: Perform Create, Read, Update, and Delete operations on the data. CTAS (Create Table As Select): Utilize CTAS to create new tables based on query results. Advanced SQL Queries: Develop complex queries to analyze and retrieve specific data.

##Project Structure-

1. Database Setup.

   🧩 Entity Relationship Diagram

2. Database Creation: Created a database named Library_Management_System.
   
3. Table Creation: Created tables for branches, employees, members, books, issued status, and return status. Each table includes relevant columns and relationships.

CREATE DATABASE library_db;

DROP TABLE IF EXISTS branch;
CREATE TABLE branch
(
            branch_id VARCHAR(10) PRIMARY KEY,
            manager_id VARCHAR(10),
            branch_address VARCHAR(30),
            contact_no VARCHAR(15)
);


-- Create table "Employee"
DROP TABLE IF EXISTS employees;
CREATE TABLE employees
(
            emp_id VARCHAR(10) PRIMARY KEY,
            emp_name VARCHAR(30),
            position VARCHAR(30),
            salary DECIMAL(10,2),
            branch_id VARCHAR(10),
            FOREIGN KEY (branch_id) REFERENCES  branch(branch_id)
);


-- Create table "Members"
DROP TABLE IF EXISTS members;
CREATE TABLE members
(
            member_id VARCHAR(10) PRIMARY KEY,
            member_name VARCHAR(30),
            member_address VARCHAR(30),
            reg_date DATE
);



-- Create table "Books"
DROP TABLE IF EXISTS books;
CREATE TABLE books
(
            isbn VARCHAR(50) PRIMARY KEY,
            book_title VARCHAR(80),
            category VARCHAR(30),
            rental_price DECIMAL(10,2),
            status VARCHAR(10),
            author VARCHAR(30),
            publisher VARCHAR(30)
);



-- Create table "IssueStatus"
DROP TABLE IF EXISTS issued_status;
CREATE TABLE issued_status
(
            issued_id VARCHAR(10) PRIMARY KEY,
            issued_member_id VARCHAR(30),
            issued_book_name VARCHAR(80),
            issued_date DATE,
            issued_book_isbn VARCHAR(50),
            issued_emp_id VARCHAR(10),
            FOREIGN KEY (issued_member_id) REFERENCES members(member_id),
            FOREIGN KEY (issued_emp_id) REFERENCES employees(emp_id),
            FOREIGN KEY (issued_book_isbn) REFERENCES books(isbn) 
);



-- Create table "ReturnStatus"
DROP TABLE IF EXISTS return_status;
CREATE TABLE return_status
(
            return_id VARCHAR(10) PRIMARY KEY,
            issued_id VARCHAR(30),
            return_book_name VARCHAR(80),
            return_date DATE,
            return_book_isbn VARCHAR(50),
            FOREIGN KEY (return_book_isbn) REFERENCES books(isbn)
);

2. CRUD Operations

• Create: Inserted sample records into the books table.
• Read: Retrieved and displayed data from various tables.
• Update: Updated records in the employees table.
• Delete: Removed records from the members table as needed.

Task 1. Create a New Book Record -- "978-1-60129-456-2', 'To Kill a Mockingbird', 'Classic', 6.00, 'yes', 'Harper Lee', 'J.B. Lippincott & Co.')"

INSERT INTO books(isbn, book_title, category, rental_price, status, author, publisher)
VALUES('978-1-60129-456-2', 'To Kill a Mockingbird', 'Classic', 6.00, 'yes', 'Harper Lee', 'J.B. Lippincott & Co.');
SELECT * FROM books;

Task 2: Update an Existing Member's Address

UPDATE members
SET member_address = '125 Oak St'
WHERE member_id = 'C103';

Task 3: Delete a Record from the Issued Status Table -- Objective: Delete the record with issued_id = 'IS121' from the issued_status table.

DELETE FROM issued_status
WHERE   issued_id =   'IS121';

Task 4: Retrieve All Books Issued by a Specific Employee -- Objective: Select all books issued by the employee with emp_id = 'E101'.

SELECT * FROM issued_status
WHERE issued_emp_id = 'E101'

Task 5: List Members Who Have Issued More Than One Book -- Objective: Use GROUP BY to find members who have issued more than one book.

SELECT
    issued_emp_id,
    COUNT(*)
FROM issued_status
GROUP BY 1
HAVING COUNT(*) > 1

3. CTAS (Create Table As Select)

• Task 6: Create Summary Tables: Used CTAS to generate new tables based on query results - each book and total book_issued_cnt**

CREATE TABLE book_issued_cnt AS
SELECT b.isbn, b.book_title, COUNT(ist.issued_id) AS issue_count
FROM issued_status as ist
JOIN books as b
ON ist.issued_book_isbn = b.isbn
GROUP BY b.isbn, b.book_title;

4. Data Analysis & Findings

The following SQL queries were used to address specific questions:

Task 7: Retrieve All Books in a Specific Category:

SELECT * FROM books
WHERE category = 'Classic';

8. Task 8: Find Total Rental Income by Category:

SELECT 
    b.category,
    SUM(b.rental_price),
    COUNT(*)
FROM 
issued_status as ist
JOIN
books as b
ON b.isbn = ist.issued_book_isbn
GROUP BY 1

9. Task 9:List Members Who Registered in the Last 180 Days:

SELECT * FROM members
WHERE reg_date >= CURRENT_DATE - INTERVAL '180 days';