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

创建学生表:CREATE TABLE Student([br][/br]Sno char(6),[br][/br]Sname varchar(8),[br][/br]Ssex char(2),[br][/br]Sbirth DATE,[br][/br]Sdept varchar(30)[br][/br]);[br][/br]现在要添加主键的代码正确的是( )。 A: ALTER TABLE student ADD PRIMARY KEY(Sno); B: ALTER TABLE student ADD PRIMARY KEY Sno ; C: ALTER TABLE student ADD unique (Sno); D: ALTER TABLE student PRIMARY KEY(Sno);

如果学生表STUDENT是使用下面的SQL语句创建的CREATE TABLE STUDENT( SNO varchar(4) PRIMARY KEY,SNAME varchar(8),SEX char(2),AGE int CHECK(AGE>15 AND AGE<30))则下面的语句中可以正确执行的是( )。 A: INSERT INTO STUDENT(SNO,SEX,AGE)values(‘S9’, ’男’, 17) B: INSERT INTO STUDENT(SNO,SEX,AGE)values(‘S9’, ‘男’, 14) C: INSERT INTO STUDENT(SNO,SEX,AGE)values(‘男’, 20) D: INSERT INTO STUDENT(SNO,SEX,AGE)values(‘S9’,‘安琦’, 16)

中国大学MOOC: 将Student表中的Sno属性定义为主码，下面空格处应填写（ ）。Create Table Student （Sno char(9) , Sname char(20) Not Null, Sex Char(2) )

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（ ）。