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