053-380

Which of the following statements best describes Flashback Versions Query?
A. Flashback Versions Query is used to make changes to multiple versions of data that existed between two points in time.
B. Flashback Versions Query is used to view all version changes on rows that existed between the time the query was executed and a point in time in the past.
C. Flashback Versions Query is used to view version changes and the SQL to undo those changes on rows that existed between two points in time.
D. Flashback Versions Query is used to view all version changes on rows that existed between two points in time.

　　Flashback Versions Query does not change data at all,so option A is incorrect.B could be correct,but only if one of the specified points in time was the current timestamp.Therefore,B is not the best description.Option C is incorrect because Flashback Versions Query does not provide the SQL to undo the changes.

posted @ 2017-11-13 15:27  巴啦啦大魔王  阅读(95)  评论(0)  编辑  收藏  举报