Improved queries for A4.

- Changed column names for better understanding
- Changed dates in inserted data to show all fine cases
- Added comments in procdure and changed variable names

Practical/Assignment-A4+A5/Queries-A4.md

@@ -4,19 +4,19 @@
 
 ```sql
 CREATE TABLE Borrower (
-  Roll_no NUMBER(15),
-  Name VARCHAR(255),
-  DateOfIssue DATE,
-  NameOfBook VARCHAR(255),
-  Status VARCHAR(255),
-  PRIMARY KEY(Roll_no)
+  roll_no INT,
+  issuer_name VARCHAR(255),
+  issue_date DATE,
+  book_name VARCHAR(255),
+  status VARCHAR(1),
+  PRIMARY KEY (roll_no)
 );
 
 CREATE TABLE Fine (
-  Roll_no NUMBER(15),
-  DateOfReturn DATE,
-  Amount NUMBER(15),
-  FOREIGN KEY(Roll_no) REFERENCES Borrower(Roll_no)
+  roll_no INT,
+  return_date DATE,
+  amt INT,
+  FOREIGN KEY (roll_no) REFERENCES Borrower (roll_no)
 );
 
 ```
@@ -24,71 +24,63 @@ CREATE TABLE Fine (
 ## Inserting data
 
 ```sql
-INSERT INTO Borrower (Roll_no, Name, DateOfIssue, NameOfBook, Status) values (1, 'Ayush Kalaskar', TO_DATE('2024-07-28','YYYY-MM-DD'), 'DBMS', 'I');
-
-INSERT INTO Borrower (Roll_no, Name, DateOfIssue, NameOfBook, Status) values (2, 'Himanshu Patil', TO_DATE('2024-07-01','YYYY-MM-DD'),'IOT', 'I');
-
-INSERT INTO Borrower (Roll_no, Name, DateOfIssue, NameOfBook, Status) values (3, 'Kshitij', TO_DATE('2024-08-05','YYYY-MM-DD'), 'TOC', 'I');
+INSERT INTO Borrower VALUES (1, 'Kalas', TO_DATE('2024-10-19', 'YYYY-MM-DD'), 'DBMS', 'I');
+INSERT INTO Borrower VALUES (2, 'Himanshu', TO_DATE('2024-10-01', 'YYYY-MM-DD'), 'TOC', 'I');
+INSERT INTO Borrower VALUES (3, 'MEPA', TO_DATE('2024-10-25', 'YYYY-MM-DD'), 'IoT', 'I');
+INSERT INTO Borrower VALUES (4, 'Kshitij', TO_DATE('2024-10-29', 'YYYY-MM-DD'), '1984', 'I');
 
 ```
 
 ## Procedure
+
 ```sql
 DECLARE
-  p_nameofbook VARCHAR(255);
-  p_rollno NUMBER(15) := 1;
-  p_dateofissue DATE;
-  currentdate DATE;
-  noofdays NUMBER(15);
-  amount NUMBER(15);
+  p_roll NUMBER; -- specify roll number here since Live SQL cannot take input from user
+  -- Eg. p_roll NUMBER := 1 will take roll number 1 as input
+  p_book VARCHAR2(255); -- specify book name here since Live SQL cannot take input from user
+  -- Eg. p_book VARCHAR2(255) := 'DBMS'
+  p_issueDate DATE;
+  totalDays NUMBER;
+  currentDate DATE;
+  fineAmt NUMBER;
   nodata EXCEPTION;
 
 BEGIN
-  p_nameofbook := '&p_nameofbook';
-  currentdate := SYSDATE;
-
-  IF p_rollno <= 0 THEN
+  -- Check if roll number is valid
+  IF (p_roll <= 0) THEN
     RAISE nodata;
   END IF;
 
-  SELECT DateOfIssue
-  INTO p_dateofissue
-  FROM Borrower
-  WHERE Roll_no = p_rollno AND NameOfBook = p_nameofbook;
+  -- Storing values from table in variables
+  SELECT issue_date INTO p_issueDate FROM Borrower WHERE roll_no = p_roll AND book_name = p_book;
 
-  SELECT TRUNC(SYSDATE) - p_dateofissue
-  INTO noofdays
-  FROM dual;
+  -- Getting the total days since book issue
+  SELECT TRUNC(SYSDATE) - p_issueDate INTO totalDays FROM dual;
 
-  DBMS_OUTPUT.PUT_LINE('No of days: ' || noofdays);
-  IF (noofdays > 30) THEN
-    amount := noofdays * 50;
-  ELSIF (noofdays >= 15 AND noofdays <= 30) THEN
-    amount := noofdays * 5;
+  -- Calculating fine
+  IF (totalDays > 30) THEN
+    fineAmt := totalDays * 50; -- Rs. 50 per day for total days greater than 30
+  ELSIF (totalDays BETWEEN 15 AND 30) THEN
+    fineAmt := totalDays * 5; -- Rs. 5 per day for total days between 15 and 30
   ELSE
-    amount := 0;
+    fineAmt := 0;
   END IF;
 
-  IF amount > 0 THEN
-    INSERT INTO Fine (Roll_no, DateOfReturn, Amount)
-    VALUES (p_rollno, SYSDATE, amount);
-  END IF;
-
-  IF amount > 0 THEN
-    UPDATE Borrower
-    SET Status = 'R'
-    WHERE Roll_no = p_rollno;
+  -- Inserting data into Fine table
+  IF fineAmt > 0 THEN
+    DBMS_OUTPUT.PUT_LINE('Roll no. ' || p_roll || ' has been fined Rs. ' || fineAmt || ' for being ' || totalDays || ' days late.');
+    INSERT INTO Fine VALUES (p_roll, SYSDATE, fineAmt);
+  ELSE
+    DBMS_OUTPUT.PUT_LINE('Roll no. ' || p_roll || ' does not have to pay any fine.');
   END IF;
+  UPDATE Borrower SET status = 'R' WHERE roll_no = p_roll AND book_name = p_book;
 
 EXCEPTION
   WHEN nodata THEN
-    DBMS_OUTPUT.PUT_LINE('Roll number or book name not found.');
-  WHEN NO_DATA_FOUND THEN
-    DBMS_OUTPUT.PUT_LINE('No entry found for the provided roll number and book name.');
+    DBMS_OUTPUT.PUT_LINE('Roll number' || p_roll || ' not found.');
   WHEN OTHERS THEN
-    DBMS_OUTPUT.PUT_LINE('An error occurred: ' || SQLERRM);
+    DBMS_OUTPUT.PUT_LINE('An error occured. Error: ' || SQLERRM);
 
 END;
 /
-
 ```