CHARINDEX in SQL Server: find a character

CHARINDEX returns the position of a search string, starting at 1. Zero means it was not there. People use it to split email and names.

Domain after @

SELECT email,
       CASE WHEN CHARINDEX('@', email) = 0 THEN NULL
            ELSE SUBSTRING(email, CHARINDEX('@', email) + 1, 200) END AS domain
FROM Customers;

PATINDEX is the same idea with a LIKE pattern. CHARINDEX is enough for a single character.