de_notes

📚 CASE STATEMENT

The CASE statement is used in SQL to create conditional logic within a query.
It allows you to return different values based on different conditions.

---

🛠️ Basic Syntax

SELECT column1,
  CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    ELSE result3
  END AS new_column
FROM table_name;

• CASE checks conditions in order and returns the first matching result.
• If no conditions match, the ELSE value is returned.
• END closes the CASE statement and assigns an alias if needed.

Example

SELECT first_name, salary,
  CASE
    WHEN salary > 80000 THEN 'High'
    WHEN salary BETWEEN 50000 AND 80000 THEN 'Medium'
    ELSE 'Low'
  END AS salary_level
FROM employees;

• This query categorizes employees based on their salary range.

Key Points

• CASE can be used in SELECT, ORDER BY, and WHERE clauses.
• The ELSE part is optional; if omitted and no condition matches, NULL is returned.
• Useful for creating dynamic, readable results without needing multiple queries.

Additional Example

SELECT product_name, price,
  CASE
    WHEN price > 500 THEN 'Expensive'
    WHEN price BETWEEN 100 AND 500 THEN 'Moderate'
    ELSE 'Cheap'
  END AS price_category
FROM products;

• This query classifies products into price categories.

---

🎥 Video Notes

---

📝 Problem Description

Describe the problem, challenge, or topic discussed in a video related to SELECT FROM.
What concept was explained or what exercise was solved?

---

DataBase Given

---

💻 My SQL Code

-- Write your SQL code attempt or solution related to SQL COMMAND
SQL COMMAND

---

🧠 Solution Code / Explanation

SQL COMMAND

Explanation - Explain what you learned, any key takeaways, or how you solved the problem related to COMMAND._

---

⬅️ Previous: SUBQUERY WITH AGGREGATE FUNCTIONS Next ➡️ LEFT JOIN