Create a row based on a condition (column value)
You can do this with the below query:

DECLARE @Employees TABLE
(
    EmpNo INT,
    GivenName NVARCHAR(255),
    PreferredName NVARCHAR(255)
)

INSERT INTO  @Employees
VALUES (1, 'Paris', 'Paris'), (2, 'Ashley', 'Ash')

SELECT EmpNo,
    GivenName,
    PreferredName
FROM @Employees
WHERE GivenName = PreferredName
UNION ALL
SELECT EmpNo,
    GivenName,
    NULL AS PreferredName
FROM @Employees
WHERE GivenName &lt;&gt; PreferredName
UNION ALL
SELECT EmpNo,
    NULL AS GivenName,
    PreferredName
FROM @Employees
WHERE GivenName &lt;&gt; PreferredName