1·As a result of performance analysis, you created an index on the prod_name column of the prod_det table,
which contains about ten thousand rows. Later, you updated a product name in the table. How does this
change affect the index?
A) A leaf will be marked as invalid.
B) An update in a leaf row takes place.
C) The index will be updated automatically at commit.
D) A leaf row in the index will be deleted and inserted.
E) The index becomes invalid when you make any updates.
【答案是D。更新索引为什么先要删除然后插入，更新索引的具体步骤是什么，leaf row是什么。】
2·You execute the following command to audit the database activities:
SQL> AUDIT DROP ANY TABLE BY scott BY SESSION WHENEVER SUCCESSFUL;
What is the effect of this command?
A) One audit record is created for the whole session if user SCOTT successfully drops one or more tables in his
session.
B) One audit record is created for every session when any user successfully drops a table owned by SCOTT.
C) One audit record is created for each successful DROP TABLE command executed by any user to drop tables
owned by SCOTT.
D) One audit record is generated for the session when SCOTT grants the DROP ANY TABLE privilege to other users in
his session.
E) One audit record is created for each successful DROP TABLE command executed in the session of SCOTT.
【答案是A。by access 和 by session有什么区别。这里的whole session是什么意思。】
谢谢，尽量能写详细一点，还有很多问题的，不过我想能解释得清楚一些，所以就分开问了，50分一题，不算低吧。。
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1) 索引分三层，最下面一层是 leaf ,每个leaf block 包含很多 leaf row， 每个leaf row 是由键值和rowid组成，查找索引时先找到键值，再根据对应的rowid找到数据块中的数据。更新索引要先删除后插入，因为这种方式最简洁和规范。不然的话，如果你采用移动的方式会变得非常麻烦和不可控制。
2)by session在每个session中发出command只记录一次,by access则每个command都记录，这是ORACLE语法规定的。
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差不多明白了，谢谢TodayZ，给分。。
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FSDFSFDSFSF
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解析的不错哈！
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thank you, 谢谢！