ORDER BY
        CASE
            WHEN @orderBy = 'ClientName' THEN c.LastName
            WHEN @orderBy = 'EmployerName' THEN cda.Name
            WHEN @orderBy = 'EmploymentDate' THEN cda.StartDate
        END

ORDER BY
    CASE WHEN @orderBy = 'ClientName' THEN c.LastName END,
    CASE WHEN @orderBy = 'EmployerName' THEN cda.Name END,
    CASE WHEN @orderBy = 'EmploymentDate' THEN cda.StartDate END

ORDER BY
    CASE
        WHEN @orderBy = 'ClientName' THEN c.LastName
        WHEN @orderBy = 'EmployerName' THEN cda.Name
        ELSE ''
    END,
    CASE
        WHEN @orderBy = 'EmploymentDate' THEN cda.StartDate
        ELSE '19000101'
    END

ORDER BY
    CASE
        WHEN @orderBy = 'ClientName' THEN c.LastName
        WHEN @orderBy = 'EmployerName' THEN cda.Name
        --gives "yyyy-mm-ddThh:mm:ss.mmm "
        WHEN @orderBy = 'EmploymentDate' THEN CONVERT(varchar(30), cda.StartDate, 121)
    END

WHEN @orderBy = 'EmploymentDate' THEN cda.StartDate

WHEN @orderBy = 'EmploymentDate' THEN cast(cda.StartDate as VarChar)