Intermediate SQL Topics-Part 5🤝

SQL CASE 💼, SQL NULL 🚫

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🔍 What is NULL In SQL? 🚫

• NULL represents missing, unknown, or not applicable data.
• It is not zero, not an empty string, and not false.
• Think of it as a placeholder for “no value”.

📌Why Is It Important to Handle NULL Values?

Handling NULL values is a common task in various real-world scenarios where data may be incomplete or missing. In the realm of databases, NULL values serve as placeholders for uncertain or absent data.

📌Working with NULL in Queries

🔸Testing for NULL

Use IS NULL or IS NOT NULL instead of equality operators:

-- Find users with missing email
SELECT * FROM users
WHERE email IS NULL;

-- Find users with known phone numbers
SELECT * FROM users
WHERE phone_number IS NOT NULL;

🔸NULL in Conditional Expressions

SELECT 
    employee_name,
    CASE WHEN 
         bonus IS NULL THEN 'No bonus' 
    ELSE 
        'Has bonus' END AS bonus_status
FROM employees;

🔸NULL in Aggregate Functions