哪个更高效？

[liangshixing]

SELECT paperid,papermc,AVG(score) FROM Answerpaper WHERE papermc like ? GROUP BY papered,papermc
还有
SELECT papered,papermc,AVG(score) FROM Answerpaper GROUP BY papered,papermc HAVING papermc like ? 两种写法运行都能通过，哪种更高效呢？