sql 复杂查询语句一

查询至少选修了两门课程并且平均成绩大于或等于75分的学生的学号、姓名、成绩和所在班级。写出相应的SQL语句

select S.studentNo,studentName,Score,className 
	from Student S join Score on S.studentNo=Score.studentNo 
	join Course on Course.courseNo=Score.courseNo 
	join Class on S.classNo=Class.classNo 
	join (select COUNT(courseName) num,student.studentNo/*连接选棵数*/
		from Student join Score on Student.studentNo=Score.studentNo 
		join Course on Score.courseNo=Course.courseNo group by student.studentNo)
		as U on U.studentNo=S.studentNo 
	join (select AVG(score) gg ,courseNo  /*连接各课程的平均分*/
		from Score join student H on Score.studentNo=H.studentNo 
		group by courseNo) G on G.courseNo=Course.courseNo 
	where num>=2 and gg>=75  /*选择选课数大于等于2，平均分大于75的*/

Ps：COUNT 和 AVG 得放在子查询里才可以

把子查询的结果连接上去之后，再加个where就可以解决复杂查询了