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