Dimensional Modeling

一、General

1. Concept

DM / Dimensional Modeling / 维度模型	The process and outcome of designing logical database schemas created to support OLAP and data warehousing solutions.
Dimensional data structure	Target of the ETL, include Fact tables, Dimension tables, Surrogate key mapping tables.
Dimension / 维	Descriptive attributes, for query constraining and labeling, e.g.CCY, region, customer, date, gender. Dimension table 描述fact的数据，denormalized flat tables, seldom changed data.
Fact / 事实	Business measures. Measures are derived from the records in the fact table and dimensions are derived from the dimension tables.
Metadata 元数据	All the information in the data warehouse that is not the actual data itself.
grain / granularity / hierarchy / 粒度	细粒度如存取记录数，粗粒度如资产、负债

 

E.g.

2. Flow

Identify reporting grain;

Identify dimensions that apply to each facttable;

Identify measures that will populate thefact tables;

 

二、Dimension

1. 模型