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047-235

原创 Linux操作系统 作者:jbymy2000 时间:2012-03-19 14:05:03 0 删除 编辑
235. Evaluate the following CREATE TABLE commands:
CREATE TABLE orders
(ord_no NUMBER(2) CONSTRAINT ord_pk PRIMARY KEY,
ord_date DATE,cust_id NUMBER(4));
CREATE TABLE ord_items
(ord_no NUMBER(2),item_no NUMBER(3),
qty NUMBER(3) CHECK (qty BETWEEN 100 AND 200),
expiry_date date CHECK (expiry_date > SYSDATE),
CONSTRAINT it_pk PRIMARY KEY (ord_no,item_no),
CONSTRAINT ord_fk FOREIGN KEY(ord_no) REFERENCES orders(ord_no));
Why would the ORD_ITEMS table not get created?
A. SYSDATE cannot be used with the CHECK constraint.
B. The CHECK constraint cannot be used twice for the same table.
C. The BETWEEN clause cannot be used for the CHECK constraint.
D. ORD_NO and ITEM_NO cannot be used as a composite primary key because ORD_NO
is also the FOREIGN KEY.
Answer: A

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