Dev

README.md

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-# Library-Management-System-Database
+# Library Management System: Database Project
+
+## Background
+
+A local library is transitioning from traditional book-keeping to a digital system. The aim is to efficiently track books, borrowers, loans, returns, and provide insights into borrowing trends.
+
+## Objective
+
+Design and implement a relational database using MS SQL to support the library's operations and enhance querying capabilities.
+
+## Requirements
+
+### 1. Design an Entity Relationship Model (ERM) Diagram
+
+- **Entities**: Books, Borrowers, and Loans.
+- **Attributes**: Specify attributes for each entity.
+- **Relationships**: Show connections between entities.
+- **Connectivity and Cardinality**: Indicate relationship types.
+- **Keys**: Identify primary (PK).
+- **Tools**: Use ERDPlus, Lucidchart, or similar. 
+
+![Entity Relationship Diagram](E-R%20Diagram.png)
+
+### 2. Design the Relational Schema using MS SQL
+
+- **Books**:
+  - BookID (PK)
+  - Title
+  - Author
+  - ISBN
+  - Published Date
+  - Genre
+  - Shelf Location
+  - Current Status ('Available' or 'Borrowed')
+
+- **Borrowers**:
+  - BorrowerID (PK)
+  - First Name
+  - Last Name
+  - Email
+  - Date of Birth
+  - Membership Date
+
+- **Loans**:
+  - LoanID (PK)
+  - BookID (FK)
+  - BorrowerID (FK)
+  - Date Borrowed
+  - Due Date
+  - Date Returned (NULL if not returned yet)
+
+![Database Schema](relationalSchema.png)
+
+### 3. Build and Seed the Database
+
+- Construct the database in MS SQL.
+- Seed with 1000 books, 1000 borrowers, and 1000 loans. Include DML scripts for seeding in the repository.
+
+### 4. Complex Queries and Procedures
+
+- **List of Borrowed Books**: Query to retrieve all borrowed books for a specific borrower.
+- **Active Borrowers with CTEs**: Identify borrowers with 2+ borrowed books not yet returned.
+- **Borrowing Frequency using Window Functions**: Rank borrowers based on frequency.
+- **Popular Genre Analysis**: Determine the most popular genre per month.
+- **Stored Procedure - `sp_AddNewBorrower`**: Add a new borrower; handle existing emails.
+- **Database Function - `fn_CalculateOverdueFees`**: Compute overdue fees for loans.
+- **Database Function - `fn_BookBorrowingFrequency`**: Count how many times a book has been borrowed.
+- **Overdue Analysis**: List overdue books with associated borrowers.
+- **Author Popularity using Aggregation**: Rank authors by borrowing frequency.
+- **Genre Preference by Age**: Determine genre preference across age groups.
+- **Stored Procedure - `sp_BorrowedBooksReport`**: Generate a report of books borrowed within a date range.
+- **Trigger Implementation**: Log changes in book status to an `AuditLog`.
+
+### BONUS
+
+- **Weekly Peak Days**: Identify the three busiest days of the week for loans and express as a percentage of total loans.

complexQueriesAndProcedures/1.ListOfBorrowedBooks.sql

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+--1. List of Borrowed Books: Retrieve all books borrowed by a specific borrower, including those currently unreturned.
+
+declare @BorrowerId int = 7;
+SELECT Books.title, Books.author, Loans.dateBorrowed, Loans.dueDate
+FROM Loans
+JOIN Books ON Loans.bookId = Books.bookId
+WHERE Loans.borrowerId = @BorrowerId;

complexQueriesAndProcedures/10.GenrePreferenceByAgeUsingGroupByAndHaving.sql

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+--10.Genre Preference by Age using Group By and Having:
+WITH BorrowerAges AS (
+    SELECT
+        borrowerId,
+        (DATEDIFF(YEAR, dateOfBirth, GETDATE()) / 10) * 10 AS AgeBracket
+    FROM
+        Borrowers
+),
+LoanGenres AS (
+    SELECT
+        ba.AgeBracket,
+        b.genre,
+        COUNT(*) AS GenreCount
+    FROM
+        BorrowerAges ba
+        JOIN Loans l ON ba.borrowerId = l.borrowerId
+        JOIN Books b ON l.bookId = b.bookId
+    GROUP BY
+        ba.AgeBracket,
+        b.genre
+),
+RankedGenres AS (
+    SELECT
+        AgeBracket,
+        genre,
+        GenreCount,
+        ROW_NUMBER() OVER (
+            PARTITION BY AgeBracket 
+            ORDER BY GenreCount DESC, genre ASC
+        ) AS RowNum
+    FROM
+        LoanGenres
+)
+SELECT 
+    CASE 
+        WHEN AgeBracket = 0 THEN '0-10'
+        WHEN AgeBracket = 10 THEN '11-20'
+        WHEN AgeBracket = 20 THEN '21-30'
+        WHEN AgeBracket = 30 THEN '31-40'
+        WHEN AgeBracket = 40 THEN '41-50'
+        WHEN AgeBracket = 50 THEN '51-60'
+        WHEN AgeBracket >= 60 THEN '61+'
+        ELSE 'Unknown'
+    END AS AgeGroup,
+    genre,
+    GenreCount
+FROM
+    RankedGenres
+WHERE
+    RowNum = 1
+ORDER BY
+    AgeBracket;

complexQueriesAndProcedures/11.StoredProcedure-BorrowedBooksReport.sql

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+--11.Stored Procedure - Borrowed Books Report:
+CREATE PROCEDURE sp_BorrowedBooksReport
+    @StartDate DATE,
+    @EndDate DATE
+AS
+BEGIN
+    -- Query to retrieve borrowed book details within the specified date range
+    SELECT 
+        b.title AS BookTitle,
+        b.author AS Author,
+        br.firstName + ' ' + br.lastName AS BorrowerName,
+        l.dateBorrowed AS BorrowingDate
+    FROM 
+        Loans l
+        INNER JOIN Books b ON l.bookId = b.bookId
+        INNER JOIN Borrowers br ON l.borrowerId = br.borrowerId
+    WHERE 
+        l.dateBorrowed BETWEEN @StartDate AND @EndDate
+    ORDER BY 
+        BorrowingDate ASC;
+END;
+
+--Test the sp
+EXEC sp_BorrowedBooksReport 
+    @StartDate = '2024-01-01', 
+    @EndDate = '2024-01-17';

complexQueriesAndProcedures/12.TriggerImplementation.sql

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+--12.Trigger Implementation
+DROP TRIGGER IF EXISTS trg_BookStatusChange;
+GO
+CREATE TRIGGER trg_BookStatusChange ON Books
+AFTER UPDATE
+AS
+BEGIN
+	DECLARE @BookID INT;
+    DECLARE @OldStatus VARCHAR(50);
+    DECLARE @NewStatus VARCHAR(50);
+	DECLARE @StatusChange VARCHAR(100);
+ IF UPDATE(currentStatus)
+    BEGIN
+        SELECT @BookID = i.bookId, @OldStatus = d.currentStatus, @NewStatus = i.currentStatus
+        FROM inserted i
+        JOIN deleted d ON i.bookId = d.bookId;
+
+        IF (@OldStatus <> @NewStatus)
+        BEGIN
+			SET @StatusChange = 'Status changed from ' + @OldStatus + ' to ' + @NewStatus;
+            INSERT INTO AuditLog
+            VALUES (@BookID, @StatusChange, GETDATE());
+        END
+    END
+END;
+
+-- Example to update a book's status to 'Borrowed'
+UPDATE Books
+SET currentStatus = 'Borrowed'
+WHERE bookId = 1 AND currentStatus = 'Available';
+
+-- Example to update a book's status to 'Available'
+UPDATE Books
+SET currentStatus = 'Available'
+WHERE bookId = 1 AND currentStatus = 'Borrowed';
+
+-- Check the AuditLog:
+SELECT * FROM AuditLog;

complexQueriesAndProcedures/14.SQLStoredProcedureWithTempTable.sql

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+-- 14.SQL Stored Procedure with Temp Table:
+DROP PROCEDURE IF EXISTS sp_GetOverdueBooksByBorrower;
+GO
+CREATE PROCEDURE sp_GetOverdueBooksByBorrower
+AS
+BEGIN
+    -- Create a temporary table
+    CREATE TABLE #OverdueBorrowers (
+        borrowerId INT
+    );
+
+    -- Insert borrowers who have overdue books into the temporary table:
+    INSERT INTO #OverdueBorrowers (borrowerId)
+    SELECT DISTINCT l.borrowerId
+    FROM Loans l
+    WHERE l.dateReturned IS NULL AND l.dueDate < GETDATE();
+
+    -- Select the overdue books for each borrower by joining the temp table with the Loans table
+    SELECT 
+        br.borrowerId,
+        br.firstName + ' ' + br.lastName AS BorrowerName,
+        b.bookId,
+        b.title AS BookTitle,
+        l.dueDate AS DueDate
+    FROM #OverdueBorrowers obr
+    JOIN Loans l ON obr.borrowerId = l.borrowerId
+    JOIN Borrowers br ON obr.borrowerId = br.borrowerId -- Make sure to join Borrowers here
+    JOIN Books b ON l.bookId = b.bookId
+    WHERE l.dateReturned IS NULL AND l.dueDate < GETDATE();
+
+    -- Drop the temporary table
+    DROP TABLE #OverdueBorrowers;
+END;
+
+-- Test the sp:
+EXEC sp_GetOverdueBooksByBorrower;

complexQueriesAndProcedures/2.ActiveBorrowersWithCTEs.sql

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+--2.Active Borrowers with CTEs:
+WITH ActiveBorrowers AS (
+    SELECT borrowerId, COUNT(*) AS TotalLoans
+    FROM Loans
+    WHERE dateReturned IS NULL
+    GROUP BY borrowerId
+    HAVING COUNT(*) >= 2
+)
+SELECT Borrowers.*, ActiveBorrowers.TotalLoans
+FROM ActiveBorrowers
+JOIN Borrowers ON ActiveBorrowers.borrowerId = Borrowers.borrowerId;

complexQueriesAndProcedures/3.BorrowingFrequencyUsingWindowFunctions.sql

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+--3.Borrowing Frequency using Window Functions:
+SELECT Borrowers.borrowerId, Borrowers.firstName, Borrowers.lastName, COUNT(Loans.borrowerId) AS TotalLoans,
+       RANK() OVER (ORDER BY COUNT(Loans.borrowerId) DESC) AS BorrowerRank
+FROM Borrowers
+LEFT JOIN Borrowers ON Loans.borrowerId = Borrowers.borrowerId
+GROUP BY Borrowers.borrowerId, Borrowers.firstName, Borrowers.lastName;

complexQueriesAndProcedures/4.PopularGenreAnalysisUsingJoinsAndWindowFunction.sql

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+--4.Popular Genre Analysis using Joins and Window Functions:
+DECLARE @Month INT=4;
+DECLARE @Year INT=2022;
+SELECT genre, COUNT(*) AS TotalLoans, 
+       RANK() OVER (ORDER BY COUNT(*) DESC) AS GenreRank
+FROM Loans
+JOIN Books ON Loans.bookId = Books.bookId
+WHERE MONTH(dateBorrowed) = @Month AND YEAR(dateBorrowed) = @Year
+GROUP BY genre;

complexQueriesAndProcedures/5.StoredProcedure-AddNewBorrowers.sql

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+--5.Stored Procedure - Add New Borrowers:
+CREATE PROCEDURE sp_AddNewBorrower
+    @FirstName VARCHAR(255),
+    @LastName VARCHAR(255),
+    @Email VARCHAR(255),
+    @DateOfBirth DATE,
+    @MembershipDate DATE
+AS
+BEGIN
+    IF EXISTS (SELECT Borrowers.borrowerId FROM Borrowers WHERE email = @Email)
+    BEGIN
+        SELECT 'Error: A borrower with this email already exists.' AS ErrorMessage;
+    END
+    ELSE
+    BEGIN
+        INSERT INTO Borrowers
+        VALUES (@FirstName, @LastName, @Email, @DateOfBirth, @MembershipDate);
+        SELECT SCOPE_IDENTITY() AS NewBorrowerID;
+    END
+END;
+
+-- Test the procedure by executing it
+EXEC sp_AddNewBorrower 
+    @FirstName = 'John',
+    @LastName = 'Doe',
+    @Email = 'john.doe@example.com',
+    @DateOfBirth = '1990-05-15',
+    @MembershipDate = '2023-04-15';

complexQueriesAndProcedures/6.DatabaseFunction-CalculateOverdueFees.sql

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+--6.Database Function - Calculate Overdue Fees
+drop function if exists fn_CalculateOverdueFees;
+go
+CREATE FUNCTION fn_CalculateOverdueFees (@LoanID INT)
+RETURNS MONEY
+AS
+BEGIN
+    DECLARE @DateBorrowed DATE;
+    DECLARE @DueDate DATE;
+    DECLARE @DateReturned DATE;
+    DECLARE @OverdueDays INT;
+    DECLARE @OverdueFee MONEY = 0;
+
+    -- Retrieve loan dates
+    SELECT @DateBorrowed = dateBorrowed, @DueDate = dueDate, @DateReturned = dateReturned
+    FROM Loans
+    WHERE loanId = @LoanID;
+
+    -- Calculate overdue days
+    IF @DateReturned IS NULL
+        SET @DateReturned = GETDATE();
+
+    SET @OverdueDays = DATEDIFF(DAY, @DueDate, @DateReturned);
+
+    -- Calculate fees based on the overdue days
+    IF @OverdueDays > 0
+    BEGIN
+        IF @OverdueDays <= 30
+            SET @OverdueFee = @OverdueDays * 1.00;
+        ELSE
+            SET @OverdueFee = (30 * 1.00) + ((@OverdueDays - 30) * 2.00);
+    END
+
+    RETURN @OverdueFee;
+END;
+
+
+
+--Test the function:
+SELECT dbo.fn_CalculateOverdueFees(1) AS OverdueFee;

complexQueriesAndProcedures/7.DatabaseFunction-BookBorrowingFrequency.sql

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+--7.Database Function - Book Borrowing Frequency:
+
+CREATE FUNCTION fn_BookBorrowingFrequency (@BookID INT)
+RETURNS INT
+AS
+BEGIN
+    RETURN( 
+		SELECT COUNT(*)
+		FROM Loans
+		WHERE bookId = @BookID
+	);
+END;
+
+
+SELECT dbo.fn_BookBorrowingFrequency(1) AS BorrowingFrequency;

complexQueriesAndProcedures/8.OverdueAnalysis.sql

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+--8.Overdue Analysis: List all books overdue by more than 30 days with their associated borrowers.
+
+SELECT b.*,bo.*,
+    DATEDIFF(DAY, l.dueDate, GETDATE()) AS DaysOverdue
+FROM 
+    Loans l
+    JOIN Books b ON l.bookId = b.bookId
+    JOIN Borrowers bo ON l.borrowerId = bo.borrowerId
+WHERE 
+    l.dateReturned IS NULL AND 
+    DATEDIFF(DAY, l.dueDate, GETDATE()) > 30;

complexQueriesAndProcedures/9.AuthorPopularityUsingAggregation.sql

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+--9.Author Popularity using Aggregation:
+
+SELECT
+    b.author,
+    COUNT(l.loanId) AS BorrowingCount,
+    RANK() OVER (ORDER BY COUNT(l.loanId) DESC) AS AuthorRank
+FROM
+    Books b
+    LEFT JOIN Loans l ON b.bookId = l.bookId
+GROUP BY
+    b.author