071考試是OCP認證的一個重要科目，不少考生都在這里受傷，對此我們專門收集整理了近期071考試的原題，并對071題庫進行了講解，希望幫助大家順利通過071考試。
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071考試原題分享-第57題、choose two:
Examine the structure of the DEPARTMENTS table
You execute the following command:
SQL> ALTER TABLE departments
SET UNUSED (country);
Which two statements are true?
A) A new column, COUNTRY, can be added to the DEPARTMENTS table after executing the command.
B) Indexes created on the COUNTRY column exist until the DROP UNUSED COLUMNS command is executed.
C) Unique key constraints defined on the COUNTRY column are removed.
D) Synonyms existing on the DEPARTMENTS table would have to be re-created.
E) Views created on the DEPARTMENTS table that include the COUNTRY column are automatically
modified and remain valid.
Answer：AC
(注意：列一旦被設置為 unused 以后，基于該列的約束、索引都被刪除，同時相關的視圖
被無法訪問。經過實驗，可以馬上往該表添加名字一樣的列，有關 set unsed 的知識點考題
前面也有出現過，本題一個特點就是答案 A)
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