3个表即学生表S、课程表C和学生选课表SC，它们的结构如下： S(S#，SN，SEX，AGE，DEPT)C(C#，CN)SC(S#，C#，GRADE)其中：S#为学号，SN为姓名，SEX为性别，AGE为年龄，DEPT为系别，C#为课程号，CN为课程名，GRADE为成绩。检索选修课程名称为“DB”的男生中的最高成绩，正确的SELECT语句是____。 A: SELECT MAX(GRADE) FROM SC WHERE CN='DB’ AND SEX='男' B: SELECT MAX(GRADE) FROM SC，C，SWHERE CN='DB' AND SEX='男' C: SELECT MAX(GRADE) FROM SC，S WHERE SC D: =C E: AND CN='DB' AND SEX='男' F: SELECT MAX(GRADE) FROM SC，C，SWHERE SC G: =C H: AND SS I: =S.S J: AND CN='DB' AND SEX='男'

查询成绩在60-80之间的学生信息，正确的语句是？ A: db.students.find({"score":{$gte:60,$lte:80}}) B: db.students.find({"score":{$gte:80},{"score":{$lte:60}}}) C: db.students.find({"score":{$gte:60},{"score":{$te:80}}}) D: db.students.find({"score":{$gt:80},{"score":{$lt:60}}})

下面 语句和”select * from student where sex=’男’ && age=20;”语句查询出的结果是一样的。（ ） A: select * from student where sex=’男’ or age=20; B: select * from student where sex=’男’ || age=20; C: select * from student where sex=’男’ and age=20; D: select * from student where sex,age in(’男’,20);

数据库中有一张表名称为Student，有列Name，Age，IDCard，Sex。要求查询所有男同学信息，下列哪个SQL语句是正确的 A: Select * From Student Where Sex '男' B: Select * From Student Where Sex ='女' C: Select * From Student Where Sex In '男' D: Select * From Student Where Sex ='男'

Studies in single-sex schools show that ______. A: smaller class brings lower achievements of the students B: special attention encourages the students to do better in class C: single sex is the only factor that influences the students' behaviors D: single sex helps the students learn more in class