删除外键约束的语句是 （ ） 。
A: delete foreign key
B: delete key FK
C: drop foreign key
D: drop key FK
A: delete foreign key
B: delete key FK
C: drop foreign key
D: drop key FK
举一反三
- 修改数据表结构语句中，用于删除外键的字句是（ ） A: delete primary key B: delete foreignkey C: drop primary key D: drop foreign key
- 要删除外键，应使用哪条语句？ A: ALTER TABLE B: DELETE TABLE C: ALTER FOREIGN KEY D: DELETE FOREIGN KEY
- 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
- 阅读下列代码: alter table表名 ____ foreign key 外键名; 若想删除外键,则需要在空白处填写 A: alter B: delete C: drop D: truncate
- 2. 以下哪个关键字可以定义外键约束。（） A: Primary Key B: Unique key C: Default Key D: Foreign Key