PL/SQL IF Statements 🚦¶

Mentor's Note: Life is full of decisions. "IF it rains, take an umbrella." In PL/SQL, IF statements give your code the ability to make decisions based on data. Without them, your code just runs in a straight line. 💡

🌟 The Scenario: The Traffic Light 🛑¶

Condition: Is the light Red, Yellow, or Green?
Logic:
- IF Red -> Stop.
- ELSIF Yellow -> Slow Down.
- ELSE -> Go! ✅

💻 1. IF-THEN (The Simple Choice)¶

The most basic form. It only does something if the condition is TRUE.

DECLARE
   v_score NUMBER := 85;
BEGIN
   IF v_score > 70 THEN
      DBMS_OUTPUT.PUT_LINE('Congratulations! You passed! 🎓');
   END IF;
END;

💻 2. IF-THEN-ELSE (The Either/Or)¶

Gives you an alternative if the condition is FALSE.

DECLARE
   v_salary NUMBER := 20000;
BEGIN
   IF v_salary > 50000 THEN
      DBMS_OUTPUT.PUT_LINE('High Income 💎');
   ELSE
      DBMS_OUTPUT.PUT_LINE('Regular Income 🛒');
   END IF;
END;

💻 3. IF-THEN-ELSIF (The Multi-Choice)¶

Used for multiple conditions. Note: In Oracle, it's spelled ELSIF (no second 'E').

DECLARE
   v_marks NUMBER := 45;
BEGIN
   IF v_marks >= 80 THEN
      DBMS_OUTPUT.PUT_LINE('Grade: A 🏆');
   ELSIF v_marks >= 60 THEN
      DBMS_OUTPUT.PUT_LINE('Grade: B ✨');
   ELSIF v_marks >= 40 THEN
      DBMS_OUTPUT.PUT_LINE('Grade: C 👍');
   ELSE
      DBMS_OUTPUT.PUT_LINE('Grade: F (Fail) ❌');
   END IF;
END;

🛡️ 4. Nested IFs & NULLs (Architect's Note)¶

Parentheses: Oracle doesn't require parentheses around the condition, but use them if your logic is complex.
The NULL Trap: If a condition is IF (v_val = 10), and v_val is NULL, the condition is neither TRUE nor FALSE—it is UNKNOWN.
Tip: Always handle NULLs using NVL or IS NULL within your IF logic to prevent "skipping" code unexpectedly.

🎨 Visual Logic: The Decision Tree¶

graph TD
    A[Start] --> B{Condition?}
    B -- True --> C[Execution Path 1]
    B -- False --> D{Next Condition?}
    D -- True --> E[Execution Path 2]
    D -- False --> F[ELSE Path]
    C --> G[End IF]
    E --> G
    F --> G