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？（）

多项选择题 需要在备忘录中记录的问题有（）。

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