下列 SQL 语句select * from student where sno = '05880101'union select * from student where sno = '05880102'与此查询语句等价的选项是( )。 A: select * from student where sno= '05880101' and sno= '05880102' B: select * from student where sno= '05880101' or sno= '05880102' C: select * from student where sno= '05880101' D: select * from student where sno= '05880102'

​如果在“学生-课程”数据库中，希望当删除Student表中的元组时，级联删除SC表中相应的元组，则在定义SC表时，应有语句____________________。‎ A: FOREIGN KEY (Sno) ON DELETE CASCADE Student(Sno) B: FOREIGN KEY (Sno) ON DELETE NO ACTION Student(Sno) C: FOREIGN KEY (Sno) REFERENCES Student(Sno) ON DELETE NO ACTION D: FOREIGN KEY (Sno) REFERENCES Student(Sno) ON DELETE CASCADE

下列SQL语句中,能够实现“收回用户user1对学生表中学号的修改权限”的是( )。 A: REVOKE UPDATE on student(sno) from ALL B: REVOKE UPDATE on student(sno) from user1 C: REVOKE UPDATE(sno) on student from user1 D: REVOKE UPDATE(sno) on student from PUBLIC

查找学生表student中姓名的第二个字为“t”的学生学号sno和姓名sname，下面SQL语句正确的是（）。 A: SELECT sno, sname FROM student WHERE sname='_t%'; B: SELECT sno, sname FROM student WHERE sname LIKE '_t%'; C: SELECT sno, sname FROM student WHERE sname＝'%t_'; D: SELECT sno, sname FROM student WHERE sname LIKE '%t_';

对于学生信息表：student(sno，sname，sex，age，grade)，查询学习成绩为空的学生的学号和姓名，下面语句正确的是 A: SELECT sno，sname FROM student WHERE grade=NULL B: SELECT sno，sname FROM student WHERE grade IS NULL C: SELECT sno，age FROM student WHERE grade IS NULL D: SELECT sno，age FROM student WHERE grade=NULL

在学生选课数据库中，查询选修了课程的学生的学号、姓名，SQL语句可为（ ） A: SELECT DISTINCT Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno; B: SELECT Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno; C: SELECT DISTINCT Sno, DISTINCT Sname FROM Student WHERE Student.Sno IN (SELECT Sno FROM SC); D: SELECT Sno, Sname FROM Student WHERE Student.Sno IN (SELECT DISTINCT Sno FROM SC);

select * from student where sno=’05880101’ union select * from student where sno=’05880102’ 与此查询语句等价的选项是（ ）。

如果有学生表student，sno代表学号，sage代表年龄，则想要得到年龄在18到20之间的学生学号的SQL语句是（） A: SELECT sno<br/>FROM student<br/>WHERE sage&gt;18 or sage&lt;20 B: SELECT sno<br/>FROM student<br/>WHERE sage=18 C: SELECT sno<br/>FROM student<br/>WHERE sage in (18,20) D: SELECT sno<br/>FROM student<br/>WHERE sage between18 and 20

查询每个学生的学号、姓名、选修的课程名及成绩，下列（)的操作是正确的。 A: select student,sno,sname,grade from student,sc where student.sno=sc.sno and sc.cno=course.cno B: select student,sno,sname,grade from student,sc,cource where student.sno=sc.sno C: select student,sno,sname,grade from student,sc,cource where sc.cno=course.cno D: select student,sno,sname,grade from student,sc,cource where student.sno=sc.sno and sc.cno=course.cno

关系模式：Student（Sno, Sname, Age）,其中Sno、Sname、Age分别表示学生的学号、姓名和年龄。“查询年龄大于20岁的学生姓名”的关系代数表达式是（） A: σSname(σage>20(Student)) B: ΠSname(σage>20(Student)) C: σSname(Πage>20(Student)) D: ΠSno(σage>20(Student))