单选题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

第1题：

以下（）语句从表TABLE_NAME中提取前10条记录。

• A、select * from TABLE_NAME where rowcount=10
• B、select TOP 10 * from TABLE_NAME
• C、select TOP of 10 * from TABLE_NAME
• D、select * from TABLE_NAME where rowcount<=10

第2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;

第3题：

您需要从方案中的雇员表中删除EMP_FK_DEPT约束条件。应使用哪条语句（）

• A、DROP CONSTRAINT EMP_FK_DEPT FROM雇员
• B、DELETE CONSTRAINT EMP_FK_DEPT FROM雇员
• C、ALTER TABLE雇员DROP CONSTRAINT EMP_FK_DEPT
• D、ALTER TABLE雇员REMOVE CONSTRAINT EMP_FK_DEPT

第4题：

以下（）语句从表TABLE_NAME中提取前10条记录。

• A、select*from TABLE_NAME where rowcount=10
• B、selectTOP 10*from TABLE_NAME
• C、selectTOPof 10*from TABLE_NAME
• D、select*from TABLE_NAME wherer owcount<=10

第5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;

第6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);

第7题：

Examine the following statement that is used to modify the constraint on the SALES table： SQL> ALTER TABLE SALES MODIFY CONSTRAINT pk DISABLE VALIDATE； Which three statements are true regarding the above command（）

• A、The constraint remains valid.
• B、The index on the constraint is dropped.
• C、It allows the loading of data into the table using SQL*Loader.
• D、New data conforms to the constraint， but existing data is not checked
• E、It allows the data manipulation on the table using INSERT/UPDATE/DELETE SQL statements.

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第13题：

删除PRIMARYKEY约束条件及其所有依赖约束条件的语法是什么（）

• A、ALTER TABLE table_name DROP CONSTRAINT constraint_name CASCADE
• B、ALTER TABLE table_name DROP CONSTRAINT FOREIGN KEY CASCADE
• C、DROP CONSTRAINT table_name（constraint_name）
• D、ALTER TABLE table_name DROP CONSTRAINT constraint_name

第14题：

A constraint in a table is defined with the INITIALLY IMMEDIATE clause. You executed the ALTER TABLEcommand with the ENABLE VALIDATE option to enable the constraint that was disabled.  What are the twoeffects of this command（）

• A、It fails if any existing row violates the constraint.
• B、It does not validate the existing data in the table.
• C、It enables the constraint to be enforced at the end of each transaction.
• D、It prevents insert， update， and delete operations on the table while the constraint is in the process of beingenabled

第15题：

如下能正确执行的语句是（）

• A、select * from table_name where 1<=2
• B、truncate table table_name
• C、delete from table_name where null=null
• D、alter table table_name add column idd int

第16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;

第17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);

第18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);

第19题：

Examine the following statement that is used to modify the primary key constraint on the SALES table： SQL> ALTER TABLE SALES MODIFY CONSTRAINT pk DISABLE VALIDATE； Which three statements aretrue regarding the above command（）

• A、The constraint remains valid.
• B、The index on the constraint is dropped.
• C、It allows the loading of data into the table using SQL *Loader.
• D、New data conforms to the constraint， but existing data is not checked.
• E、It allows the data manipulation on the table using INSERT/UPDATE/DELETE SQL statements.

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