程名称和分数selectsts
cc
scscorefromsstsccoursecwherescs
osts
oa
dscc
occ
oa
dscscore70（30）求选了课程的学生人数selectcou
tdisti
cts
ofromsc（31）查询不同课程成绩相同的学生的学号、课程号、学生成绩selectafromscascbwhereascorebscorea
dac
obc
o（32）检索至少选修两门课程的学生学号selects
ofromscgroupbys
ohavi
gcou
ts
o1（33）查询两门以上不及格课程的同学的学号及其平均成绩selects
oavgscorefromscwheres
oi
selects
ofromscwherescscore60groupbys
ohavi
gcou
ts
o1groupbys
o
fr