Chapter 8- Data Warehouse and Data Mart Modeling
Snowflake Models
a star schema that contains the dimensions that are normalized
Transaction Time
a column representing the time of the transaction
Transaction Identifier
a column representing the transaction ID
Row Indicator
a column that provides a quick indicator of whether the record is currently valid
Dimensional Modeling
a data design methodology used for designing subject-oriented analytical databases, ie, data warehouses or data marts
Normalized Data Warehouse
a data warehouse modeled by using the traditional database modeling techniques of ER modeling, relational modeling, and/or normalization, resulting in a normalized set of tables
Slowly Changing Dimensions
a dimension that contains attributes whose values can change
Detailed Fact Tables
a fact table in which each record refers to a single fact
Type 2 Approach
an approach to handling slowly changing dimensions that is used in cases when history should be preserved; it creates a new additional dimension record using a new value for the surrogate key every time a value in a dimension record changes
Type 3 Approach
an approach to handling slowly changing dimensions used in cases when there is a fixed number of changes possible per column of a dimension, or in cases when only a limited history is recorded; it creates a "previous" and "current" column in the dimension table, for each column where the changes are anticipated
Degenerate Dimension
an event identifier included within the fact table (Rather than having its own separate dimension)
Timestamps
columns in tables that indicate the time interval for which the values in the records are applicable
Detailed Data
data composed of single instances of data
Aggregated Data
data representing summarization of multiple instances of data
Aggregated Fact Tables
fact tables in which each record summarizes multiple facts
Star Schema
schema containing fact tables and dimensions
Conformed Dimensions
standardized dimensions created before development of star schemas; typically used with multiple fact tables
Constellation (Galaxy) of Stars
star schema containing multiple fact tables
Dimension Tables (dimensions)
tables in a dimensional model that contain descriptions of the business, organization, or enterprise to which the subject of analysis belongs and contain a primary key and attributes that are used for analysis of the measures in the fact tables
Fact Tables
tables in a dimensional model that contain measures related to the subject of analysis and foreign keys that connect the fact table to the dimension tables
Type 1 Approach
the approach to handling slowly changing dimensions based on overwriting values in records of dimensions; it is used mostly when a change in a dimension is the result of an error
Dimensionally Modeled Data Warehosue
data warehouse modeled using dimensional modeling
Granularity
describes what is depicted by one row in the fact table
Line-Item Detailed Fact Table
a fact table in which each record represents a line item of a particular transaction
Transaction-Level Detailed Fact Table
a fact table in which each row represents a particular transaction
Surrogate Key
a noncomposite system-generated key assigned to each dimension of a star schema
