单项选择题 In your test database， you have created the ORDERS table as an index­organized table （IOT）. To facilitate faster querying， you have created a mapping table and a bitmap index on the ORDER_FILLED column. You observe that the query performance degrades when users perform a large volume of transactions.  While investigating the reason， you find that the mapping table segment is fragmented， leading to poor performance. Which option would you use to defragment the mapping table without affecting the original table data？（）

单项选择题 You are designing an application for a telecom company and you have been asked to design a database table to facilitate monthly bill generation. The bill would include details of customer calls， listed in chronological order.  Which method would you follow to achieve this objective without increasing the overhead of sorting the rows？（）

单项选择题 Inyourdatawarehousingapplication，yougeneratereportsfrequently.Thedataisstaticinthetablesbeingusedtogeneratereports.Youarecurrentlyusingjoins，resultinginalargeperformanceoverhead.Whatkindofdatabasestructurewouldyouusetoreducetheresponsetimeofthequery？（）