设教学数据库中有三个关系：
学生关系S(SNO,SNAME,AGE,SEX,DEPT)
选课关系SC(SNO,CNO,GRADE)
课程关系C(CNO,CNAME,CREDIT)
试用SQL描述下列查询：
1. 查询选修了课程号为C2课程,且这门课程的成绩在80到90分之间的学生学号,姓名与成绩；
2.查询概率统计成绩前10名的学生学号与姓名；
3. 查询至少选修了课程号为C2和C4课程的学生学号；
4. 查询选修了课程号为C1但不选修C2课程的学生学号；
5.查询既不修课程号为C1也不修课程号为C2课程的学生学号、姓名和年龄；
6.查询所选课程的成绩均在80以上的学生学号和姓名；
7.查询所修课程的平均分前三名,且所选课程均及格,所修课程20门以上的企管系男生的学生的学号和姓名,平均分；
8.查询选修所有了学号为330105204010学生所修课程的学生的学号、姓名、性别；
9. 查询获得总学分最高的前10名学生的学号,姓名,总学分。
(我不太清楚你说的课程号是指CNO还是CNAME,我这里假定你说的课程号为CNO，以下语句均未考虑字段数值类型)
1、SELECT A1.SNO,A1.SNAME,A2.GRADE FROM S A1,SC A2 WHERE A1.SNO = A2.SNO AND A2.CNO = C2 AND A2.GRADE BETWEEN 80 AND 90
2、不太懂
3、SELECT A1.SNO FROM SC A1,SC A2 WHERE A1.SNO = A2.SNO AND A1.CNO = C2 AND
A2.CNO = C4 GROUP BY A1.SNO
4、SELECT A1.SNO FROM SC A1 WHERE A1.CNO = C1 AND A1.SNO NOT IN (SELECT SNO FROM SC WHERE CNO = C2)
5、SELECT A1.SNO,A1.SNAME,A1.AGE FROM S A1,SC A2 WHERE A1.SNO = A2.SNO AND A2.CNO NOT IN(C1,C2)
6、SELECT SNO,SNAME FROM S WHERE SNO NOT IN(
SELECT SNO FROM SC WHERE GRADE <= 80 ) GROUP BY SNO
7、
1、SELECT A1.SNO,A1.SNAME,A2.GRADE FROM S A1,SC A2 WHERE A1.SNO = A2.SNO AND A2.CNO = C2 AND A2.GRADE BETWEEN 80 AND 90
2、不太懂
3、SELECT A1.SNO FROM SC A1,SC A2 WHERE A1.SNO = A2.SNO AND A1.CNO = C2 AND
A2.CNO = C4 GROUP BY A1.SNO
4、SELECT A1.SNO FROM SC A1 WHERE A1.CNO = C1 AND A1.SNO NOT IN (SELECT SNO FROM SC WHERE CNO = C2)
5、SELECT A1.SNO,A1.SNAME,A1.AGE FROM S A1,SC A2 WHERE A1.SNO = A2.SNO AND A2.CNO NOT IN(C1,C2)
6、SELECT SNO,SNAME FROM S WHERE SNO NOT IN(
SELECT SNO FROM SC WHERE GRADE <= 80 ) GROUP BY SNO
7、
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