【单选题】某多电子原子的四个电子分别具有下列各组量子数:(1)2,0,0,+1/2;(2)2,1,0,-1/2;(3)3,1,1,-1/2;(4)3,1,-1,+1/2;它们能量的高低顺序为:( )
【单选题】在choose表创建成功后,再为choose表添加外键约束,约束名为choose_student_fk,外键为student_no,参照 student表的stuednt_no字段,以下命令正确的是( )。
A.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no);
B.
alter table choose add constraint choose_student_fk REFERENCES student(stu_no);
C.
alter table choose add constraint choose_student_fk FOREIGN KEY (stu_no) REFERENCES student(student_no);
D.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) REFERENCES student(stu_no);
【单选题】为choose表添加外键约束,约束名为choose_student_fk,外键为student_no,参照 student表的st_no字段,以下SQL语句片段正确的是( )。
A.
constraint choose_student_fk FOREIGN KEY (student_no);
B.
constraint choose_student_fk FOREIGN KEY (student_no) REFERENCES student(st_no);
C.
constraint choose_student_fk FOREIGN KEY (st_no) REFERENCES student(student_no);
D.
constraint choose_student_fk REFERENCES student(st_no);
【单选题】为choose表添加外键约束,约束名为choose_student_fk,外键为student_no,连接到 student表的stuednt_no字段,以下命令正确的是( )
A.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) REFERENCES student;
B.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) REFERENCES student(stuednt_no);
C.
alter table choose add constraint choose_student_fk REFERENCES student(stuednt_no);
D.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) ;
【判断题】两栖纲迷齿亚纲中的一支最有可能进化出了爬行动物。
【判断题】直流电机如果将励磁绕组与电枢绕组,同时反接,就能改变转向。( )
【单选题】某女,足月产 3次,流产1次,无早产,现有子女2人,请写出其生育史( )
【单选题】在choose表创建成功后,再为choose表添加外键约束,约束名为choose_student_fk,外键为student_no,参照 student表的stud_no字段,以下命令正确的是( )。
A.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no);
B.
alter table choose add constraint choose_student_fk REFERENCES student(stud_no);
C.
alter table choose add constraint choose_student_fk FOREIGN KEY (stud_no) REFERENCES student(student_no);
D.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) REFERENCES student(stud_no);
【单选题】六堡茶是广西特产,其品质素以( )四绝而著称 。
【单选题】为choose表添加外键约束,约束名为choose_student_fk,外键为student_no,连接到 student表的stuednt_no字段,以下命令正确的是( )。
A.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) ;
B.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) REFERENCES student(stuednt_no);
C.
alter table choose add constraint choose_student_fk FOREIGN KEY (student_no) REFERENCES student;
D.
alter table choose add constraint choose_student_fk REFERENCES student(stuednt_no);