Podcast
Questions and Answers
What does the attribute hierarchy provide in the context of data warehousing?
What does the attribute hierarchy provide in the context of data warehousing?
- A complex algorithm for data compression.
- A shorthand vocabulary to define the grain of each cube. (correct)
- An encryption key for securing sensitive data.
- A detailed map of the physical storage structure.
In data warehousing, what does it mean to 'line up all the hierarchies for a given star on a single diagram'?
In data warehousing, what does it mean to 'line up all the hierarchies for a given star on a single diagram'?
- To prepare the data for encryption.
- To create a backup of the data warehouse.
- To physically rearrange the data for faster access.
- To document the attribute hierarchies and aggregation level represented by a cube. (correct)
Which schema consists of a fact table and a group of dimension tables, with each dimension table joined directly to the fact table?
Which schema consists of a fact table and a group of dimension tables, with each dimension table joined directly to the fact table?
- Galaxy schema
- Constellation schema
- Star schema (correct)
- Snowflake schema
What is the result called when the relationships between dimension attributes are made explicit in a dimensional design?
What is the result called when the relationships between dimension attributes are made explicit in a dimensional design?
How does snowflaking a dimension relate to normalization in database design?
How does snowflaking a dimension relate to normalization in database design?
In the context of data warehousing, what is the primary drawback of using normalization techniques like snowflaking?
In the context of data warehousing, what is the primary drawback of using normalization techniques like snowflaking?
What is a key characteristic of dimensional models in relation to relational databases?
What is a key characteristic of dimensional models in relation to relational databases?
What is the purpose of precomputing the various combinations of dimension values and fact values in a cube?
What is the purpose of precomputing the various combinations of dimension values and fact values in a cube?
What is a primary advantage of using a multidimensional database compared to a relational database for data warehousing?
What is a primary advantage of using a multidimensional database compared to a relational database for data warehousing?
Which term describes the process of interactively changing the perspective on data, such as adding or removing attributes, and receiving immediate feedback?
Which term describes the process of interactively changing the perspective on data, such as adding or removing attributes, and receiving immediate feedback?
In the context of OLAP, what does it mean to 'slice and dice' data?
In the context of OLAP, what does it mean to 'slice and dice' data?
How does interacting with a star schema typically differ from interacting with a cube in a multidimensional database?
How does interacting with a star schema typically differ from interacting with a cube in a multidimensional database?
Which of the following describes the primary function of ETL in data warehousing?
Which of the following describes the primary function of ETL in data warehousing?
In a star schema loading process, what is the significance of loading dimension tables before fact tables?
In a star schema loading process, what is the significance of loading dimension tables before fact tables?
What is the first step in loading dimension tables during the ETL process?
What is the first step in loading dimension tables during the ETL process?
What is the purpose of surrogate keys in dimension tables?
What is the purpose of surrogate keys in dimension tables?
What is the primary goal of processing fact tables during the ETL process?
What is the primary goal of processing fact tables during the ETL process?
What step is essential before loading records into the fact table?
What step is essential before loading records into the fact table?
Which operation is performed on facts to ensure they match the grain of the fact table?
Which operation is performed on facts to ensure they match the grain of the fact table?
Which of the following is a key characteristic of OLAP interaction with a cube?
Which of the following is a key characteristic of OLAP interaction with a cube?
What is the significance of 'normalization' in database design?
What is the significance of 'normalization' in database design?
Which of the following steps is a standard practice as a project is loading dimension tables?
Which of the following steps is a standard practice as a project is loading dimension tables?
In the context of data warehousing, what does 'Drilling' generally refer to?
In the context of data warehousing, what does 'Drilling' generally refer to?
Which statement best explains why normalization is typically avoided in analytical databases?
Which statement best explains why normalization is typically avoided in analytical databases?
What is a significant advantage to dimensional models being deployed on Multi-dimensional Databases?
What is a significant advantage to dimensional models being deployed on Multi-dimensional Databases?
If you're 'slicing and dicing' a data cube, what are you trying to accomplish?
If you're 'slicing and dicing' a data cube, what are you trying to accomplish?
What is a core function of the 'Fact' table in a star schema?
What is a core function of the 'Fact' table in a star schema?
In a star schema, what is the primary role of the dimension tables?
In a star schema, what is the primary role of the dimension tables?
During ETL, why is it useful to 'extract source data from source(s)'?
During ETL, why is it useful to 'extract source data from source(s)'?
During dimensional modelling processes, what are 'surrogate keys' used for?
During dimensional modelling processes, what are 'surrogate keys' used for?
What could possibly cause an ETL process to fail during the Fact Table Processing?
What could possibly cause an ETL process to fail during the Fact Table Processing?
Given that you are utilizing a star schema in your data warehouse, which action would be the MOST critical during the data loading process?
Given that you are utilizing a star schema in your data warehouse, which action would be the MOST critical during the data loading process?
Suppose you need to represent 'order dollars' in your cube, but your source data tracks orders at the product and day level. What do you need to consider?
Suppose you need to represent 'order dollars' in your cube, but your source data tracks orders at the product and day level. What do you need to consider?
You've implemented a data warehouse with a star schema but notice query performance is degrading. Which design change would MOST quickly help?
You've implemented a data warehouse with a star schema but notice query performance is degrading. Which design change would MOST quickly help?
You're tasked with designing an ETL process for a data warehouse. Your source system contains historical snapshots of customer data which are slowly changing, but you're only tracking the very latest version. Which approach is MOST suitable for loading dimension tables?
You're tasked with designing an ETL process for a data warehouse. Your source system contains historical snapshots of customer data which are slowly changing, but you're only tracking the very latest version. Which approach is MOST suitable for loading dimension tables?
Which of the following represents the correct order of operations in a typical ETL process?
Which of the following represents the correct order of operations in a typical ETL process?
What does the acronym MDB stand for in the context of data warehousing?
What does the acronym MDB stand for in the context of data warehousing?
In data warehousing, what is meant by a 'cube'?
In data warehousing, what is meant by a 'cube'?
Flashcards
Dimensional Design
Dimensional Design
A design approach for data warehouses focused on organizing data into dimensions and facts for analysis.
Hierarchies & Drilling
Hierarchies & Drilling
Navigating through levels of detail in a data hierarchy to gain insights.
Attribute hierarchy
Attribute hierarchy
Provides a shorthand way to define the level of detail stored in a data cube.
Star Schema
Star Schema
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Snowflake
Snowflake
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Operational System
Operational System
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Normalization
Normalization
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Cube
Cube
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Multidimensional Database (MDB)
Multidimensional Database (MDB)
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Precompute
Precompute
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Online Analytical Processing (OLAP)
Online Analytical Processing (OLAP)
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OLAP Interaction
OLAP Interaction
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Dimensional models
Dimensional models
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Slice and Dice
Slice and Dice
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ETL
ETL
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Foreign key references
Foreign key references
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Extract source data
Extract source data
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Idenitfy changes and records
Idenitfy changes and records
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Order of operation for fact tables
Order of operation for fact tables
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Study Notes
Hierarchies & Drilling
- The attribute hierarchy provides a shorthand way to define the grain of each cube.
- A cube can hold order dollars at the brand (product) and quarter (day) levels.
- Aligning hierarchies on a single diagram and drawing a horizontal line defines the aggregation level of a cube.
Snowflakes
- A star schema is composed of a fact table and a group of dimension tables, each directly connected to the fact table.
- A snowflake schema results when dimension attributes are explicitly detailed in a dimensional design.
- Snowflaking is like normalization, which guides the design of operational systems.
- Normalization is not ideal for analytic settings because it is meant for operational systems supporting varied, simultaneous transactions that facilitate data modifications.
- Analytic databases do not share the same usage pattern as operational systems, making normalization unnecessary.
- Unnecessary complexity from normalization detracts from usability, complicates ETL, and can negatively affect performance and does not guarantee data integrity.
Cubes
- Dimensional models are not always in relational databases.
- A multidimensional database (MDB) uses a cube to store dimensional information.
- The main concept of a cube is to precompute combinations of dimension and fact values for interactive study.
Multidimensional vs Relational Storage
- Multidimensional databases have the advantage of speed.
- Cubes let users modify their data perspective by adding or removing attributes, with immediate feedback.
- This process is known as Online Analytical Processing (OLAP).
- OLAP interaction with a cube enables slicing, dicing, drilling up, and drilling down with instantaneous feedback.
- Star schemas use a require a query-and-response paradigm, so each change requires a new query.
Star Schema
- A star schema includes a fact table and dimension tables, directly connected.
Loading a Star Schema
- Each row in the fact table has foreign key references to rows in dimension tables.
- Dimension rows must be ready before a fact table row can be inserted.
- Dimension processing happens first, then fact table processing.
Loading Dimension Tables
- Loading dimension tables involves extracting source data, assembling dimensional attributes, identifying new/changed dimension records, managing surrogate keys, processing new records, and processing type 1 and 2 SCD changes.
Loading Fact Tables
- Loading fact tables includes extracting data from source systems, computing facts, aggregating facts to match grain, obtaining surrogate keys, and loading fact table records.
ETL Tools
- Pentaho
- Alteryx
- Talend Data Preparation
- ClearStory Data
- Dataiku
- Datameer
- Datawatch
- Informatica REV
- Paxata
- Platfora
- Sagent DataFlow
- Trifacta
- SAP Agile Data Preparation
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