COALESCE in SQL Server

COALESCE returns the first argument that is not NULL. You can pass three or four. ISNULL only takes two. See also <a href="/tsql/isnull">ISNULL</a>.

Something we can contact

SELECT customer_id, first_name,
       COALESCE(NULLIF(LTRIM(RTRIM(phone)), ''), email, 'No contact') AS contact
FROM Customers;

NULLIF turns a blank phone into NULL so COALESCE can skip it and try email.