Star vs Snowflake Schema Types Quiz

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Questions and Answers

What is the central component of a star schema?

  • The foreign keys
  • The fact table (correct)
  • The query reporting attributes
  • The dimension tables

What is the primary purpose of the fact table in a star schema?

  • To support ad-hoc information needs
  • To store the decision analysis attributes (correct)
  • To contain classification and aggregation information
  • To link to the dimension tables via foreign keys

What is the relationship between the dimension tables and the fact table in a star schema?

  • Many-to-many
  • One-to-many (correct)
  • One-to-one
  • Many-to-one

Which of the following best describes the purpose of dimension tables in a star schema?

<p>To provide classification and aggregation information (D)</p> Signup and view all the answers

How are dimensions used in querying a star schema?

<p>To aggregate the numerical values in the fact table (D)</p> Signup and view all the answers

Which of the following is not a main characteristic of a star schema?

<p>The dimension tables have a many-to-many relationship with the fact table (D)</p> Signup and view all the answers

What is a key characteristic of a Star schema?

<p>Fact table surrounded by dimension tables (A)</p> Signup and view all the answers

Which type of schema design involves expanding dimension tables into multi-tables?

<p>Snowflake Schema (D)</p> Signup and view all the answers

What does a Multi-fact star model represent in dimensional modeling?

<p>Multiple fact tables surrounded by dimensions (A)</p> Signup and view all the answers

Why is a Star schema considered to have a simple design compared to a Snowflake schema?

<p>Deals with less data redundancy (A)</p> Signup and view all the answers

In the context of dimensional modeling, what is a common characteristic of fact tables?

<p>Contain detailed business events such as sales and expenses (A)</p> Signup and view all the answers

Why are conformed dimensions important in multi-fact star models?

<p>To reduce the number of joins required in queries (A)</p> Signup and view all the answers

What are the two types of columns found in fact tables in dimensional modeling?

<p>Keys and measures (C)</p> Signup and view all the answers

What is the grain of a measurement in a fact table?

<p>The level of detail in the measurement (D)</p> Signup and view all the answers

What does the key column in a fact table consist of?

<p>Foreign keys to dimensional tables (C)</p> Signup and view all the answers

In a dimensional model, where is ninety-percent of the data typically located?

<p>Fact tables (A)</p> Signup and view all the answers

Which type of relationship exists between fact tables and dimensions in dimensional modeling?

<p>One-to-many (C)</p> Signup and view all the answers

What is the purpose of the measures in a fact table?

<p>Represent actual business activity (B)</p> Signup and view all the answers

Flashcards

Star Schema

A data warehouse design with a central fact table linked to surrounding dimension tables.

Fact Table

The central table holding metrics and measures in a star schema; stores the facts of the business.

Dimension Table

Tables that describe and classify the data in a fact table across business attributes.

Keys (Fact Table)

Foreign keys linking the fact table to dimension tables, enabling analysis.

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Measures (Fact Table)

Actual measurements of business activity (e.g., sales revenue).

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Grain (Measure)

Level of detail in a measure (e.g., daily, weekly).

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Conformed Dimensions

Shared dimensions used in multiple fact tables for consistency.

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Multi-fact Star Models

Star schemas with multiple fact tables, handling diverse business events.

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Dimension Characteristics

Properties like de-normalization and redundancy inherent in dimension tables.

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De-normalization

Data redundancy strategies used to reduce data joins.

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Data redundancy

Duplicate information within a data warehouse or database

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Data Warehouse

Systemized storage of business information from multiple sources.

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Business Intelligence

Methods used to evaluate business data and gain insights.

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Decision Analysis

Applying data to support strategic business choices.

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Foreign Key (FK)

A column in one table that refers to the primary key of another table.

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Primary Key

Uniquely identifies a record in a table.

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Operational Metrics

Measures of daily business activities for operational efficiency.

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Business Events

Activities that drive business metrics and can be measured.

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Fact

An organizational performance measure or metric.

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Datamarts

Subset of a data warehouse containing specific data for a department.

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Study Notes

Star Schema

  • A star schema consists of a central fact table surrounded by dimension tables, connected via foreign keys.
  • The fact table contains a large number of rows corresponding to observed facts and external links.
  • The fact table contains descriptive attributes for decision analysis and query reporting, and foreign keys to link to dimension tables.

Fact Table

  • Contains performance measures, operational metrics, and aggregated measures (e.g., sales volumes, customer retention rates, profit margins).
  • Primarily addresses what the data warehouse supports for decision analysis.
  • Contains two types of columns: keys and measures.

Keys in Fact Table

  • Consist of a group of foreign keys (FK) that point to the primary keys of dimensional tables.
  • Enable business analysis.

Measures in Fact Table

  • Represent actual measures of business activity (e.g., sales revenue, order quantity).
  • Each measurement has a grain, which is the level of detail in the measurement of an event (e.g., unit of measure, currency used, ending daily balance).
  • Examples: SalesQuantity, SalesAmount, ReturnAmount, ReturnQuantity, DiscountAmount, DiscountQuantity, and TotalCost.

Dimension Tables

  • Contain classification and aggregation information about the central fact rows.
  • Contain attributes that describe the data contained within the fact table.
  • Address how data will be analyzed and summarized.
  • Have a one-to-many relationship with rows in the central fact table.

Dimension Characteristics

  • Represented by one table in a star schema.
  • De-normalized data structure.
  • High level of data redundancy.
  • Maintenance is difficult.
  • Good for datamarts with simple relationships (1:1 or 1:many).

Multi-fact Star Models

  • Examples of dimensional models depict a single fact table surrounded by dimensions, but reality requires multiple facts.
  • Multiple facts are often necessary (e.g., sales, expenses, inventory, and other business events).
  • Shared dimensions are referred to as conformed dimensions.

Fact Table Characteristics

  • A fact is also referred to as an organizational performance measure.
  • Fact contains redundancy.
  • Ninety-percent of the data in a dimensional model is typically located in the fact tables.
  • Key design concerns include minimizing and standardizing data, and making it consistent.

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