PL/SQL Data Types 🏗️

Mentor's Note: In standard SQL, we have columns like VARCHAR2 or NUMBER. PL/SQL supports all of those, plus some special types like BOOLEAN and Anchored Types. Anchored types are the "Secret Sauce" of Oracle—they make your code future-proof! 💡

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🌟 The Scenario: The Custom Mold 🧱

Imagine you are a baker.

• Fixed Size: You have a 10cm cake tin. (VARCHAR2(10)).
• Anchored Size: You tell your assistant: "Make the tin the exact same size as the customer's order." If the customer changes the order size, your tin changes automatically. ✅

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💻 1. Scalar Types (The Basics)

Scalar types hold a single value.

• VARCHAR2(n): Text.
• NUMBER(p, s): Numeric.
• DATE: Date and time.
• BOOLEAN: TRUE, FALSE, or NULL. (Only in PL/SQL, not in SQL columns!).

DECLARE
   v_is_active BOOLEAN := TRUE;
   v_score     NUMBER(3) := 95;
BEGIN
   IF v_is_active THEN
      DBMS_OUTPUT.PUT_LINE('User is online! ✅');
   END IF;
END;

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💻 2. Anchored Types (%TYPE) ⚓

This is the most professional way to declare variables. Instead of guessing the size of a column, you "anchor" your variable to the database column.

DECLARE
   -- "Make v_emp_name the same type as the 'first_name' column in 'employees'"
   v_emp_name employees.first_name%TYPE;
   v_salary   employees.salary%TYPE;
BEGIN
   SELECT first_name, salary INTO v_emp_name, v_salary
   FROM employees WHERE employee_id = 101;
END;

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🛡️ 3. Why use %TYPE? (Architect's Note)

1. Maintenance: If the DBA changes first_name from 50 chars to 100 chars, your PL/SQL code will not break. It updates automatically! ⚡
2. Safety: You avoid "Value too large" errors because your variable will always be large enough to hold the table data.
3. Accuracy: You never have to worry about data type mismatches (e.g., trying to put a Number into a String).

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🎨 Visual Logic: The Link

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📈 Learning Path

• ← Back: Constants
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