这段代码可以改写成group by...having语句吗?如果能,怎么改?

SELECT empfname, empsalary FROM qemp
WHERE empsalary <
 (SELECT .90*AVG(empsalary) FROM qemp);

SELECT empfname, empsalary FROM qemp GROUP BY empsalary HAVING empsalary > 90*AVG(empsalary);

select empfname,empsalary from qemp
group by empsalary
having empsalary < .90*avg(empsalary)

不能groupby在empfname上

SELECT 1 AS flg, empfname,empsalary
FROM qemp
GROUP BY flg
HAVNG empsalary < .90*avg(empsalary)

上面我写的也不对 应该是不能用groupby