单选题Which statement adds a constraint that ensures the CUSTOMER_NAME column of the CUSTOMERS table holds a value?（）A ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;B ALTER TABLE customers MODIFY CONSTRAINT cust_name_nn CH

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单选题

Which statement adds a constraint that ensures the CUSTOMER_NAME column of the CUSTOMERS table holds a value?（）

ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

ALTER TABLE customers MODIFY CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn NOT NULL;

ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn IS NOT NULL;

ALTER TABLE customers MODIFY name CONSTRAINT cust_name_nn NOT NULL;

ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name NOT NULL;

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第1题：

Which statement adds a constraint that ensures the CUSTOMER_NAME column of the CUSTOMERS table holds a value?()

A. ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

B. ALTER TABLE customers MODIFY CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

C. ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn NOT NULL;

D. ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn IS NOT NULL;

E. ALTER TABLE customers MODIFY name CONSTRAINT cust_name_nn NOT NULL;

F. ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name NOT NULL;

参考答案：C

第2题：

Which statement describes VRRP object tracking?()

A.It monitors traffic flow and link utilization.

B.It ensures the best VRRP router is the virtual router master for the group.

C.It causes traffic to dynamically move to higher bandwidth links

D.It thwarts man-in-the-middle attacks.

参考答案：B

第3题：

The OPTIMIZER_USE_PLAN_BASELINES parameter is set to TRUE. The optimizer generates a plan for a SQL statement but does not find a matching plan in the SQL plan baseline.Which two operations are performed by the optimizer in this scenario?（）

A. The optimizer adds the new plan to the plan history.

B. The optimizer selects the new plan for the execution of the SQL statement.

C. The optimizer adds the new plan to the SQL plan baseline as an accepted plan.

D. The optimizer adds the new plan to the SQL plan baseline but not in the ENABLED state.

E. The optimizer costs each of the accepted plans in the SQL plan baseline and picks the one with the lowest cost.

参考答案：A, E

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 syntax turns an existing constraint on?（）

A、ALTER TABLE table_name ENABLE constraint_name;
B、ALTER TABLE table_name STATUS = ENABLE CONSTRAINT constraint_name;
C、ALTER TABLE table_name ENABLE CONSTRAINT constraint_name;
D、ALTER TABLE table_name STATUS ENABLE CONSTRAINT constraint_name;
E、ALTER TABLE table_name TURN ON CONSTRAINT constraint_name;

正确答案:C

第6题：

Which syntax turns an existing constraint on? ()

A. ALTER TABLE table_name ENABLE constraint_name;

B. ALTER TABLE table_name STATUS = ENABLE CONSTRAINT constraint _ name;

C. ALTER TABLE table_name ENABLE CONSTRAINT constraint _ name;

D. ALTER TABLE table_name TURN ON CONSTRAINT constraint _ name;

参考答案：C

第7题：

Which statement describes VRRP object tracking?（）

A、It monitors traffic flow and link utilization.
B、It ensures the best VRRP router is the virtual router master for the group.
C、It causes traffic to dynamically move to higher bandwidth links
D、It thwarts man-in-the-middle attacks.

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：

Evaluate the CREATE TABLE statement： CREATE TABLE products （product_id NUMBER （6） CONSTRAINT prod_id_pk PRIMARY KEY， product_name VARCHAR2 （15））； Which statement is true regarding the PROD_ID_PK constraint？（）

A、 It would be created only if a unique index is manually created first.
B、 It would be created and would use an automatically created unique index.
C、 It would be created and would use an automatically created nonunique index.
D、 It would be created and remains in a disabled state because no index is specified in the command.

正确答案:B

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

Which statement adds a constraint that ensures the CUSTOMER_

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