COALESCE - Handling NULLs

COALESCE returns the first non-NULL value from a list of arguments.

It's perfect for providing default values:

SELECT first_name, COALESCE(email, 'No email') AS email
FROM employees;

If email is NULL, it shows 'No email' instead.

You can chain multiple fallbacks:

COALESCE(phone, mobile, 'No contact')

This checks phone first, then mobile, then uses the default.

COALESCE is supported in all major SQL databases and is the standard way to handle NULLs in output.