单选题PO_DETAILS表包含以下列： PO_NUM NUMBER NOT NULL, Primary Key PO_LINE_ID NUMBER NOT NULL, Primary Key PRODUCT_ID NUMBER Foreign Key to PRODUCT_ID column of the PRODUCTS table QUANTITY NUMBER UNIT_PRICE NUMBER(5,2) 请评估以下语句： ALTER TABLE po_details DISABLE CONSTRAINT po_details_pk CASCADE;此语句用于完成什么任务（）A新创建一个对PO_NUM列的PRIMARYKEY约束条件B删除并重新创建对PO_NUM列的PRIMARYKEY以及FOREIGNKEY的约束条件C禁用依赖于PO_NUM列的所有FOREIGNKEY约束条件D禁用对PO_NUM列的约束条件，同时创建PRIMARYKEY索引
单选题
PO_DETAILS表包含以下列： PO_NUM NUMBER NOT NULL, Primary Key PO_LINE_ID NUMBER NOT NULL, Primary Key PRODUCT_ID NUMBER Foreign Key to PRODUCT_ID column of the PRODUCTS table QUANTITY NUMBER UNIT_PRICE NUMBER(5,2) 请评估以下语句： ALTER TABLE po_details DISABLE CONSTRAINT po_details_pk CASCADE;此语句用于完成什么任务（）
A
新创建一个对PO_NUM列的PRIMARYKEY约束条件
B
删除并重新创建对PO_NUM列的PRIMARYKEY以及FOREIGNKEY的约束条件
C
禁用依赖于PO_NUM列的所有FOREIGNKEY约束条件
D
禁用对PO_NUM列的约束条件，同时创建PRIMARYKEY索引
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