OCP-1Z0-051-題目解析-第1題

1. View the Exhibit and examine the structure of the SALES, CUSTOMERS, PRODUCTS, and TIMES tables.

The PROD_ID column is the foreign key in the SALES table, which references the PRODUCTS table.

Similarly, the CUST_ID and TIME_ID columns are also foreign keys in the SALES table referencing the CUSTOMERS and TIMES tables,

respectively.

Evaluate the following CREATE TABLE command:

CREATE TABLE new_sales(prod_id, cust_id, order_date DEFAULT SYSDATE)ASSELECT prod_id, cust_id, time_idFROM sales;

Which statement is true regarding the above command? 

題目翻譯：查看並檢查銷售、客戶、產品、日期表的結構。PROD_ID是銷售表參考產品表的外鍵，同樣的，CUST_ID和TIME_ID也是銷售表的外鍵，分別參照了客戶表和日期表，評估下面建立表的語句，CREATE……，哪一個表述是正確的？

 

A. The NEW_SALES table would not get created because the DEFAULT value cannot be specified in the column definition.

B. The NEW_SALES table would get created and all the NOT NULL constraints defined on the specifiedcolumns would be passed to the new table. 

C. The NEW_SALES table would not get created because the column names in the CREATE TABLE command and the SELECT clause do not match. 

D. The NEW_SALES table would get created and all the FOREIGN KEY constraints defined on the specified columns would be passed to the new table.

Answer: B

 答案解析：

A：不能建立表，原因是不能在定義欄位指定預設值 （錯誤，我們可以再建立表的同時，通過Default指定相關欄位的預設值）
B: 可以建立表，NOT NULL約束也可以傳遞到新表中 （正確，可以通過desc NEW_SALES 查看新表的結構）
C: 不能建立表，因為建立表的欄位名和被選中表的欄位名不一樣 （錯誤，只要是對應欄位的資料類型一致就可以了，欄位名可以不一樣）
D：可以建立表，並且所有的外鍵約束也會傳遞到新表中 （錯誤，通過desc NEW_SALES可以發現只有非空約束傳遞到了新表）