數(shù)據(jù)挖掘概念與技術原書第2版第3章數(shù)據(jù)倉庫與olap技術概述(編輯修改稿)
2025-05-27 02:58 本頁面
【文章內(nèi)容簡介】 ? 維定義 (維表 ) define dimension dimension_name as (attribute_or_subdimension_list) ? 特殊案例 (共享維表的定義 ) ? 第一次作為維表定義 “ cube definition” ? 然后： define dimension dimension_name as dimension_name_first_time in cube cube_name_first_time define cube sales_star [time, item, branch, location]: dollars_sold = sum(sales_in_dollars), avg_sales = avg(sales_in_dollars), units_sold = count(*) define dimension time as (time_key, day, day_of_week, month, quarter, year) define dimension item as (item_key, item_name, brand, type, supplier_type) define dimension branch as (branch_key, branch_name, branch_type) define dimension location as (location_key, street, city, province_or_state, country) define cube sales_snowflake [time, item, branch, location]: dollars_sold = sum(sales_in_dollars), avg_sales = avg(sales_in_dollars), units_sold = count(*) define dimension time as (time_key, day, day_of_week, month, quarter, year) define dimension item as (item_key, item_name, brand, type, supplier(supplier_key, supplier_type)) define dimension branch as (branch_key, branch_name, branch_type) define dimension location as (location_key, street, city(city_key, province_or_state, country)) define cube sales [time, item, branch, location]: dollars_sold = sum(sales_in_dollars), avg_sales = avg(sales_in_dollars), units_sold = count(*) define dimension time as (time_key, day, day_of_week, month, quarter, year) define dimension item as (item_key, item_name, brand, type, supplier_type) define dimension branch as (branch_key, branch_name, branch_type) define dimension location as (location_key, street, city, province_or_state, country) define cube shipping [time, item, shipper, from_location, to_location]: dollar_cost = sum(cost_in_dollars), unit_shipped = count(*) define dimension time as time in cube sales define dimension item as item in cube sales define dimension shipper as (shipper_key, shipper_name, location as location in cube sales, shipper_type) define dimension from_location as location in cube sales define dimension to_location as location in cube sales ? 一個數(shù)據(jù)立方體的度量是一個 數(shù)值 函數(shù)，該函數(shù)可以對數(shù)據(jù)立方體空間的每一個點求值。 ? 度量可以根據(jù)其所用的聚集函數(shù)分為三類： ? 分布的 (distributive)：將函數(shù)用于 n個聚集值得到的結果和將函數(shù)用于所有數(shù)據(jù)得到的結果一樣。 ? 比如： count()， sum()， min()， max()等 ? 代數(shù)的 (algebraic)：函數(shù)可以由一個帶 M個參數(shù)的代數(shù)函數(shù)計算（ M為有界整數(shù)），而每個參數(shù)值都可以有一個分布的聚集函數(shù)求得。 ? 比如： avg()， min_N()， standard_deviation() ? 整體的 (holistic)：描述函數(shù)的子聚集所需的存儲沒有一個常數(shù)界（無法以上述方法進行計算）。 ? 比如： median()， mode()， rank() ? 一個概念分層（ concept hierarchy）定義一個映射序列，將低層概念映射到更一般的高層概念 ? . 表示 location的概念：杭州 ?浙江 ?中國 ?亞洲 ? 概念分層允許我們在各種抽象級審查和處理數(shù)據(jù) ? 概念分層可以由系統(tǒng)用戶、領域?qū)＜?、知識工程師人工的提供，也可以根據(jù)數(shù)據(jù)分布的統(tǒng)計分析自動的產(chǎn)生 all Europe North_America Mexico Canada Spain Germany Vancouver M. Wind L. Chan ... ... ... ... ... ... all region office country Toro
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