CREATE TABLE `score` ( `id` int(11) NOT NULL AUTO_INCREMENT, `sno` int(11) NOT NULL, `cno` tinyint(4) NOT NULL, `score` tinyint(4) DEFAULT NULL, PRIMARY KEY (`id`) ) ;
以下查询语句结果一定相等的是()
A.SELECT sum(score) / count(*) FROM score WHERE cno = 2;
B.SELECT sum(score) / count(id) FROM score WHERE cno = 2;
C.SELECT sum(score) / count(sno) FROM score WHERE cno = 2;
D.SELECT sum(score) / count(score) FROM score WHERE cno = 2;
E.SELECT sum(score) / count(1) FROM score WHERE cno = 2;
F.SELECT avg(score) FROM score WHERE cno = 2;
B.SELECT sum(score) / count(id) FROM score WHERE cno = 2;
C.SELECT sum(score) / count(sno) FROM score WHERE cno = 2;
D.SELECT sum(score) / count(score) FROM score WHERE cno = 2;
E.SELECT sum(score) / count(1) FROM score WHERE cno = 2;
F.SELECT avg(score) FROM score WHERE cno = 2;