7. NULL Functions Reference

Handling missing values.

COALESCE()

Return: Value

Return first non-null argument.

Syntax signature:COALESCE(val1, val2, default)

Code snippet:

python

SELECT COALESCE(phone, email, 'N/A') FROM contacts;

Expected Output:Primary contact info.

Remember: Always ensure correct syntax formatting when calling COALESCE().

NULLIF()

Return: Value

Return null if both values match.

Syntax signature:NULLIF(val1, val2)

Code snippet:

python

SELECT NULLIF(salary, 0) FROM employees;

Expected Output:Null instead of zeros.

Remember: Always ensure correct syntax formatting when calling NULLIF().

IFNULL()

Return: Value

Replace null values with default (MySQL/SQLite).

Syntax signature:IFNULL(col, default)

Code snippet:

python

SELECT IFNULL(status, 'inactive') FROM users;

Expected Output:Default status fallback.

Remember: Always ensure correct syntax formatting when calling IFNULL().

ISNULL()

Return: Value

Check if value is null.

Syntax signature:ISNULL(col)

Code snippet:

python

SELECT * FROM logs WHERE ISNULL(message);

Expected Output:Logs with missing messages.

Remember: Always ensure correct syntax formatting when calling ISNULL().