Teel Tip - SQL

COALESCE() returns the first non-NULL value.

Why does this matter? This function will iterate through the expressions provided as arguments and provide the first value that exists. Say you want to display a user’s preferred name. Columns first_name, middle_name, and last_name are used and you want to prioritize middle_name if available, otherwise use first_name and last_name.

SELECT COALESCE(middle_name, first_name) AS display_name
FROM Customers;

If middle_name is not NULL, display_name will be the value of middle_name. Otherwise, display_name will be the value of first_name.

This is crucial when dealing with potentially incomplete data, as it allows you to provide a default or fallback value when a specific column or expression is NULL.