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Which SQL statement defines the FOREIGN KEY constraint on th

题目
单选题
Which SQL statement defines the FOREIGN KEY constraint on the DEPTNO column of the EMP table?（）
A

CREATE TABLE EMP (empno NUMBER(4), ename VARCNAR2(35), deptno NUMBER(7,2) NOT NULL CONSTRAINT emp_deptno_fk FOREIGN KEY deptno REFERENCES dept deptno);

B

CREATE TABLE EMP (empno NUMBER(4), ename VARCNAR2(35), deptno NUMBER(7,2) CONSTRAINT emp_deptno_fk REFERENCES dept (deptno));

C

CREATE TABLE EMP (empno NUMBER(4) ename VARCHAR2(35), deptno NUMBER(7,2) NOT NULL, CONSTRAINT emp_deptno_fk REFERENCES dept (deptno) FOREIGN KEY (deptno));

D

CREATE TABLE EMP (empno NUMBER(4), ename VARCNAR2(35), deptno NUMBER(7,2) FOREIGN KEY CONSTRAINT emp deptno fk REFERENCES dept (deptno));

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相似问题和答案

第1题：

Which constraint can be defines only at the column level? ()

A. UNIQUE

B. NOT NULL

C. CHECK

D. PRIMARY KEY

E. FOREIGN KEY


参考答案：B

第2题：

When defining a referential constraint between the parent table T2 and the dependent table T1, which of the following is true?()

A.The list of column names in the FOREIGN KEY clause can be a subset of the list of column names in the primary key of T2 or a UNIQUE constraint that exists on T2.

B.The list of column names in the FOREIGN KEY clause can be a subset of the list of column names in the primary key of T1 or a UNIQUE constraint that exists on T1.

C.The list of column names in the FOREIGN KEY clause must be identical to the list of column names in the primary key of T2 or a UNIQUE constraint that exists on T2.

D.The list of column names in the FOREIGN KEY clause must be identical to the list of column names in the primary key of T1 or a UNIQUE constraint that exists on T1.


参考答案：C

第3题：

Which constraint can be defined only at the column level? ()

A. UNIQUE

B. NOT NULL

C. CHECK

D. PRIMARY KEY

E. FOREIGN KEY


参考答案：B

第4题：

Which two statements are true about the primary key constraint in a table？ （）

  • A、It is not possible to disable the primary key constraint.
  • B、It is possible to have more than one primary key constraint in a single table.
  • C、The primary key constraint can be referred by only one foreign key constraint.
  • D、The primary key constraint can be imposed by combining more than one column.
  • E、The non-deferrable primary key constraint creates an unique index on the primary key column if it is not already indexed.

正确答案:D,E

第5题：

Which constraint can be defines only at the column level? （）

  • A、UNIQUE
  • B、NOT NULL
  • C、CHECK
  • D、PRIMARY KEY
  • E、FOREIGN KEY

正确答案:B

第6题：

Which statement explicitly names a constraint? ()

A. ALTER TABLE student_grades ADD FOREIGN KEY (student_id) REFERENCES students (student_id);

B. ALTER TABLE student_grades ADD CONSTRAINT NAME = student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);

C. ALTER TABLE student_grades ADD CONSTRAINT student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);

D. ALTER TABLE student grades ADD NAMED CONSTRAINT student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);

E. ALTER TABLE student grades ADD NAME student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);


参考答案：C

第7题：

Which constraint can be defined only at the column level?（）

  • A、UNIQUE
  • B、NOT NULL
  • C、CHECK
  • D、PRIMARY KEY
  • E、FOREIGN KEY

正确答案:B

第8题：

You need to modify the STUDENTS table to add a primary key on the STUDENT_ID column. The table is currently empty. Which statement accomplishes this task?()

A. ALTER TABLE students ADD PRIMARY KEY _ id;

B. ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student_id);

C. ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY student_id;

D. ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY (student_id);

E. ALTER TABLE students MODIFY CONSTRAINT stud_id_pk PRIMARY KEY (student_id);


参考答案：D

第9题：

以下SQL命令执行什么操作（） ALTER TABLE employees ADD CONSTRAINT emp_manager_fk FOREIGN KEY(manager_id) REFERENCES employees(employee_id).

  • A、更改employees表并禁用emp_manager_fk约束条件
  • B、向EMPLOYEES表添加FOREIGN KEY约束条件，要求经理必须已是雇员
  • C、向EMPLOYEES表添加FOREIGN KEY约束条件，要求经理标识应匹配每个雇员标识
  • D、更改employees表并添加FOREIGN KEY约束，要求每个雇员标识必须唯一

正确答案:C

第10题：

You need to modify the STUDENTS table to add a primary key on the STUDENT_ID column. The table is currently empty.Which statement accomplishes this task?（）

  • A、ALTER TABLE students ADD PRIMARY KEY student_id;
  • B、ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student _ id);
  • C、ALTER TABLE students ADD CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id);
  • D、ALTER TABLE students MODIFY CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id);

正确答案:C

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