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单选题 在创建表时可以根据应用要求定义属性上的约束条件,其中列值唯一的约束关键词是
学科：数据库系统概论2023
时间：2023-06-16 06:28:51
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题目1单选题
将Student表中的Sno属性定义为主码A. create table student ( sno char(9) foreign key, sname char(20) not null, ssex char(2), sage smallint, sdept char(20) )B. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2), sage smallint, sdept char(20) )C. create table student ( sno char(9) , sname char(20) primary key, ssex char(2), sage smallint, sdept char(20) )D. create table student ( sno char(9) , sname char(20) not null, ssex char(2), sage smallint, sdept char(20) )
题目2单选题
将sc表中的sno、cno属性组定义为主码A. create table sc ( sno char(9) primary key, cno char(4) primary key, grade smallint )B. create table sc ( sno char(9) primary key, cno char(4) , grade smallint )C. create table sc ( sno char(9) , cno char(4) primary key, grade smallint )D. create table sc ( sno char(9) , cno char(4) , grade smallint, primary key (sno,cno) )
题目3单选题
定义sc表中的参照完整性,sno,cno分别参照应用student表的主码和course表的主码A. create table sc ( sno char(9) not null, cno char(9) not null, grade smallint, primary key(sno,cno), foreign key (sno) references student(sno) )B. create table sc ( sno char(9) not null, cno char(9) not null, grade smallint, primary key(sno,cno), foreign key (cno) references student(cno) )C. create table sc ( sno char(9) not null, cno char(9) not null, grade smallint, primary key(sno,cno), foreign key (sno) references student(sno), foreign key (cno) references student(cno) )D. create table sc ( sno char(9) not null, cno char(9) not null, grade smallint, primary key(sno,cno) )
题目4单选题
student表的ssex只允许取"男"或"女"A. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2), sage smallint, sdept char(20) )B. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2) in('男','女'), sage smallint, sdept char(20) )C. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2) check in('男','女'), sage smallint, sdept char(20) )D. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2) check(ssex in('男','女')), sage smallint, sdept char(20) )
题目5单选题
sc表的grade的值应该在0和100之间A. create table sc ( sno char(9) , cno char(4) , grade smallint, primary key(sno,cno), foreign key(sno) references student(sno), foreign key(cno) references student(cno), )B. create table sc ( sno char(9) , cno char(4) , grade smallint check(0,100), primary key(sno,cno), foreign key(sno) references student(sno), foreign key(cno) references student(cno), )C. create table sc ( sno char(9) , cno char(4) , grade smallint check(grade>=0 and grade<=100), primary key(sno,cno), foreign key(sno) references student(sno), foreign key(cno) references student(cno), )D. create table sc ( sno char(9) , cno char(4) , grade smallint check(0 and 100), primary key(sno,cno), foreign key(sno) references student(sno), foreign key(cno) references student(cno), )
题目6单选题
当学生的性别是男时,其名字不能以Ms.打头A. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2), sage smallint, sdept char(20) )B. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2), sage smallint, sdept char(20), check(ssex='男' and sname not like 'Ms.%') )C. create table student ( sno char(9) , sname char(20) not null, ssex char(2), sage smallint, sdept char(20), check(ssex='男' and sname not like 'Ms.%') )D. create table student ( sno char(9) primary key, sname char(20) not null, ssex char(2), sage smallint, sdept char(20), check(ssex='女' or sname not like 'Ms.%') )
题目7单选题
建立学生登记表student,要求姓名不能取空值,年龄小于30,性别只能是"男"或"女"A. create table student ( sno char(9) primary key, sname char(20) , ssex char(2) constraint c3 check(ssex in('男','女')), sage smallint, sdept char(20) )B. create table student ( sno char(9) primary key, sname char(20) constraint c1 not null, ssex char(2) constraint c3 check(ssex in('男','女')), sage smallint, sdept char(20) )C. create table student ( sno char(9) primary key, sname char(20) constraint c1 not null, ssex char(2) constraint c3 check(ssex in('男','女')), sage smallint constraint c2 check(sage<30), sdept char(20) )D. create table student ( sno char(9) primary key, sname char(20) constraint c1 not null, ssex char(2) constraint c3 check(ssex in('男','女')), sage smallint constraint c2 check(sage<30), sdept char(20) check )
题目8单选题
去掉student表中对性别的限制(第7题已在student表中建立对性别的限制)A. drop table studentB. delete table studentC. alter table student drop constraintD. alter table student drop constraint c3
题目9单选题
在创建表时可以根据应用要求定义属性上的约束条件,其中列值非空的约束关键词是A. notB. not nullC. not uniqueD. not check
题目10单选题
在创建表时可以根据应用要求定义属性上的约束条件,其中列值唯一的约束关键词是A. uniqueB. nullC. not nullD. not unique
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