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PL/SQL Numeric FOR LOOP 🔢

Mentor's Note: The FOR loop is the most predictable loop. It's like a train track with a fixed start and end station. You tell it "Go from 1 to 10," and it does exactly that—no more, no less. 💡

🌟 The Scenario: The School Assembly 🎒

Imagine a teacher counting students. - Task: Count from student 1 to student 50. - Rule: You don't stop until you reach 50. - The Loop: It handles the counting for you automatically.

💻 1. The Basic Syntax

The counter variable (index) is automatically declared by the loop. You don't need to add it to your DECLARE section!

BEGIN
   -- 🚀 Logic: Start at 1, End at 5
   FOR i IN 1..5 LOOP
      DBMS_OUTPUT.PUT_LINE('Student number: ' || i);
   END LOOP;
END;

💻 2. The REVERSE Keyword 🔙

If you want to count backwards, use REVERSE. Note: The range must still be written Small..Large.

BEGIN
   -- 🚀 Logic: Count 5, 4, 3, 2, 1
   FOR i IN REVERSE 1..5 LOOP
      DBMS_OUTPUT.PUT_LINE('Countdown: ' || i);
   END LOOP;
END;

🏗️ Architect's Note: Loop Scope 🛡️

  1. Automatic Counter: The index variable i only exists inside the loop. You cannot use it after END LOOP;.
  2. Read-Only: You cannot change the value of i manually (e.g., i := i + 5 is not allowed!). Oracle manages it.
  3. Upper Bound: If the starting number is larger than the ending number (e.g., 10..1), the loop will not run at all (unless you use REVERSE).

🎨 Visual Logic: The Fixed Track

graph LR
    A[Start: 1] --> B[2]
    B --> C[3]
    C --> D[4]
    D --> E[End: 5]

📈 Learning Path