通过引入汇总表来提高一些经常执行的聚集查询的性能，这属于下列数据库应用系统开发过程中哪个阶段的任务
A、需求分析D
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Fromtheviewpointofwordformation,theword“smog”isa______.
In1900,theUnitedStatesrankedfirstintheworldintheproductionof________.
Hewasspecificallyaskedtowriteaplaythatwouldbe________tothelocalcommunity.
Weareinterestedintheweatherbecauseit_______ussodirectly—whatwewear,whatwedoandevenhowwefeel.
句子写作：”HappyChristmas“hesaid.
