Chapter 8

aggregated fact table

each record summarizes multiple facts

conformed dimension

a set of commonly used dimensions first created in a dimensionally modeled data warehouse

transaction time

adding a TIME attribute to the fact table and not in a new dimension or to the CALENDAR table (it increases too much)

Type 3

applicable in cases in which there is a fixed number of changes possible per column of a dimension; involves creating a previous and current column in the dimension table for each columns where changes are anticipated

Type 1

approach that is the simplest and used most often when a change in dimension is the result of an error; simply changes the value in the dimension's record where the new value replaces the old, NO HISTORY

dimensions

contain descriptions of the business, organization, or enterprise to which the subject of analysis belongs

dimensional modeling

data design methodology used for designing subject-oriented analytical databases

star schema

dimensional schema is referred as this

slowly changing dimensions

a dimension that contains attributes whose values can change

granularity

describes what is depicted by one row in the fact table; the "fineness" of the data

detailed data table

each record refers to a single fact

normalized data warehouse

envisions a data warehouse as an integrated analytical database modeled by using ER modeling and relational modeling, resulting in a normalized relational database schema; Inmon approach

transaction identifier

represented as sales transaction id, order id, rental id, ticket id, bill id, etc

surrogate key

simple, non-composite system-generated key in all star schema dimensional tables

transaction-level detailed fact table

each represents a particular transaction

snowflake models

if the dimensions are normalized within the dimensional model

data mart

stand-alone data warehouse created by various, independent groups in an organization

facts

table containing measures related to the subject of analysis; FK's relating to associated dimension tables

dimensionally modeled data warehouse

Kimball approach; data warehouse as a collection of dimensionally modeled intertwined data marts that integrate analytically useful information from the operational data sources

degenerate dimension

it is simpler to include an event identifier within the fact table than to create a separate dimension for it

Type 2

used in cases where history should be preserved and creates a new additional dimension record using a new value for the surrogate key every time a value in a dimension record changes; includes timestamps and row indicators

constellation

dimensional model with multiple fact tables; also called a galaxy of stars

line-item detailed fact table

each row represents a line item of a particular transaction