查询每门课程被选修的学生数SELECT sc.CId, COUNT(*)FROM scGROUP BY(sc.CId)

​下列SQL语句中，_____________可以在“学生-课程”数据库正确实现“查询选修并成绩良好3门以上课程的学生学号及其满足条件的课程门数”。‌ A: SELECT Sno，COUNT(*)FROM SCGROUP BY SnoHAVING Grade>=80 AND COUNT(*) >3 B: SELECT Sno，COUNT(*)FROM SCWHERE Grade>=80GROUP BY SnoHAVING COUNT(*) >3 C: SELECT Sno，COUNT(*)FROM SCGROUP BY SnoWHERE Grade>=80HAVING COUNT(*) >3 D: SELECT Sno，COUNT(*)FROM SCGROUP BY SnoWHERE Grade>=80 AND HAVING COUNT(*) >3

​下列SQL语句中，_________可以在“学生-课程”数据库正确实现“将学生的学号及他的平均成绩定义为一个视图”。‎ A: CREAT VIEW S_G(Sno，Gavg) AS SELECT Sno，AVG(Grade) FROM SCGROUP BY Sno； B: CREAT VIEW S_G(Sno，AVG(Grade)) AS SELECT Sno，AVG(Grade) FROM SCGROUP BY Sno； C: CREAT VIEW S_G AS SELECT Sno，AVG(Grade) FROM SCGROUP BY Sno； D: CREAT VIEW S_G(Sno，Gavg) AS SELECT Sno，AVG(Grade) FROM SCORDER BY Sno；

使用jxgl数据库，按课程号统计各门课程的平均分select cno,AVG(score)______ from SCgroup by sno______

在MySQL中,假设有学生选课表SC(sno,cno,score)。那么列出所有选修课程超过5门的学生学号以及选修课程数目,其正确的SQL语句为()。 A: select sno,count(cno)from scwhere count(cno)>=5; B: select sno,count(cno)from scgroup by sno where count(cno)>=5; C: select sno,count(cno)from scgroup by sno having count(cno)>=5; D: select sno,count(cno)from scgroup by cno having count(cno)>=5;

统计每门课程的选课人数select cno , _________from scgroup by ________ A: count(*) ; cno B: count(sno) ; cno C: count(*) ; sno D: count(sno) ; sno

（3）统计选修四门以上课程的学生的学号和总成绩(不统计不及格的课程)，并要求按总成绩降序排列出来。正确的SELECT语句是( )。 A: SELECT S B: ，SUM(GRADE) FORM SCGROUP BY S C: HAVING COUNT(*)＞＝4; D: SELECT S E: ，SUM(GRADE) FORM SCGROUP BY S F: HAVING COUNT(*)＞＝4ORDER BY SUM(GRADE) DESC; G: SELECT S H: ，SUM(GRADE) FROM SCWHERE GRADE＞=60GROUP BY S I: HAVING COUNT(*)＞＝4ORDER BY SUM(GRADE) DESC; J: SELECT S K: ，SUM(GRADE) FROM SCGROUP BY S L: HAVING GRADE＞=60 AND COUNT(*)＞＝4ORDER BY SUM(GRADE) DESC;

针对数据库S_T，以下创建视图的命令不正确的是（ ）。 A: create view view1asselect sno,avg(grade)from scgroup by sno B: create view view2asselect sno,sname,sdeptfrom studentwhere sdept='CS' C: create view view3asselect sno,sage+20from studentwhere ssex='女' D: create view view4asselect student.sno,sname,sc.sno,cno,grade from sc,studentwhere sc.sno=student.sno and cno='1'