ช่วยดู SQL ทีครับต้องการ GROUP BY แต่ไอดี แต่มันบังคับให้ GROUP BY firstname ด้วย

SELECT 
	DISTINCT
	a.questionId,
	a.firstname
FROM
(
	SELECT q.questionId, u.firstname, u.lastname, q.createdDate FROM HR_CALLCENTER.dbo.question AS q
	INNER JOIN HR_CALLCENTER.dbo.users AS u ON q.createdId = u.employeeId
	UNION
	SELECT r.questionId, u.firstname, u.lastname, r.createdDate FROM HR_CALLCENTER.dbo.reply AS r
	INNER JOIN HR_CALLCENTER.dbo.users AS u ON r.createdId = u.employeeId
) AS a

SELECT 
	DISTINCT
	a.questionId,
	a.firstname,
	MAX(q.createdDate) AS createdDate
FROM
(
	SELECT q.questionId, u.firstname, u.lastname, q.createdDate FROM HR_CALLCENTER.dbo.question AS q
	INNER JOIN HR_CALLCENTER.dbo.users AS u ON q.createdId = u.employeeId
	UNION
	SELECT r.questionId, u.firstname, u.lastname, r.createdDate FROM HR_CALLCENTER.dbo.reply AS r
	INNER JOIN HR_CALLCENTER.dbo.users AS u ON r.createdId = u.employeeId
) AS a
GROUP BY a.questionId, a.firstname