Data Modeling Quiz

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Questions and Answers

What are some risks associated with redundancies in a database?

Redundancies can compromise the consistency of the database and lead to anomalies.

What is an update anomaly in a database?

An update anomaly occurs when changing one piece of data requires multiple changes in different places.

How does normalization help prevent anomalies in a database?

Normalization helps prevent anomalies by reducing redundancies and ensuring data is stored in a structured and consistent manner.

What are the three types of data models mentioned in the text?

<p>Relational, multidimensional, and semantic</p> Signup and view all the answers

What is the purpose of the entity relationship model (ERM)?

<p>To structure communication between users and developers and as a basis for database design</p> Signup and view all the answers

What is the major disadvantage of not using a model, such as ERM, when creating relational databases?

<p>Redundant information can be stored</p> Signup and view all the answers

What is the main consequence of redundancies in a database?

<p>Compromise the consistency and can lead to anomalies.</p> Signup and view all the answers

Give an example of an update anomaly in a database.

<p>If the department number changes, several tuples must be changed at the same time.</p> Signup and view all the answers

How does normalization help prevent anomalies in a database?

<p>Normalization helps avoid redundancies and inconsistencies.</p> Signup and view all the answers

What are the advantages of using star and snowflake schemas for modeling multidimensional data spaces?

<p>Star and snowflake schemas allow performance-oriented modeling of multidimensional spaces by structuring data in a way that optimizes query performance.</p> Signup and view all the answers

What is the difference between physical, logical, and semantic data models?

<p>Physical data models specify how data is physically stored, logical data models describe data on a logical level regardless of storage, and semantic data models depict data on a technology-neutral level.</p> Signup and view all the answers

What is the purpose of the entity relationship model (ERM) in application development and database design?

<p>The entity relationship model (ERM) is used in the conceptual phase of application development to structure communication between users and developers, and as a basis for database design in the implementation phase.</p> Signup and view all the answers

What is the purpose of normalization in database design?

<p>The purpose of normalization is to eliminate redundancies and inconsistencies in data, making it more efficient to manage.</p> Signup and view all the answers

Who developed the theory of normal forms?

<p>Edgar F. Codd</p> Signup and view all the answers

What is the definition of the first normal form (1NF)?

<p>In 1NF, a table row may only contain one attribute value and the attribute value must be atomic.</p> Signup and view all the answers

What is the purpose of normalization in database design?

<p>The purpose of normalization in database design is to eliminate redundancies and inconsistencies in data, making it more efficient to manage.</p> Signup and view all the answers

What is the definition of the first normal form (1NF)?

<p>The first normal form (1NF) states that a table row may only contain one attribute value and the attribute value must be atomic.</p> Signup and view all the answers

Who developed the theory of normal forms?

<p>The theory of normal forms was developed by Edgar F. Codd, the inventor of the relational database.</p> Signup and view all the answers

What is the definition of the second normal form (2NF)?

<p>A relation is in the second normal form if it is in the first normal form and all non-key attributes depend functionally on the entire key.</p> Signup and view all the answers

What is the definition of the third normal form (3NF)?

<p>A relation is in the third normal form if the second normal form exists and no functional dependencies exist between non-key attributes.</p> Signup and view all the answers

What must be done to create a new table from attributes that only depend on a part of the compound primary key?

<p>A new table must be created from those attributes that only depend on a part of the compound primary key.</p> Signup and view all the answers

What is the focus of the online analytical processing (OLAP) cube model?

<p>The focus of the OLAP cube model is usually on business ratios as carriers of quantitative information.</p> Signup and view all the answers

What are attributes and dimensions in the OLAP cube model?

<p>Attributes are the characteristics that describe a dimension, while dimensions are sets of attributes that explain a specific aspect of the data.</p> Signup and view all the answers

What is the purpose of a relationship hierarchy in the OLAP cube model?

<p>The relationship hierarchy facilitates both the aggregation of data and navigation through the data in the OLAP cube model.</p> Signup and view all the answers

What is the display format of the result?

<p>spreadsheet-style display</p> Signup and view all the answers

What values populate row 1?

<p>values of X</p> Signup and view all the answers

What values populate column A?

<p>values of Y</p> Signup and view all the answers

What is an OLAP cube?

<p>An OLAP cube is a multi-dimensional array of data used for online analytical processing (OLAP), which is a computer-based technique of analyzing data to look for insights.</p> Signup and view all the answers

What is the difference between a cube and a hypercube?

<p>A cube is a multi-dimensional dataset, while a hypercube refers to a multi-dimensional dataset with more than three dimensions.</p> Signup and view all the answers

What is a slice in the context of an OLAP cube?

<p>A slice is a subset of the data in an OLAP cube that is generated by selecting a specific value for one dimension and only showing the data associated with that value.</p> Signup and view all the answers

What is a hierarchy in the context of an OLAP cube?

<p>A hierarchy is a set of parent-child relationships in which a parent member summarizes its children.</p> Signup and view all the answers

What are the common operations in OLAP cube analysis?

<p>The common operations in OLAP cube analysis include slice and dice, drill down, roll up, and pivot.</p> Signup and view all the answers

What is the purpose of the slice operation in OLAP cube analysis?

<p>The slice operation involves picking a rectangular subset of a cube by choosing a single value for one of its dimensions, creating a new cube with one fewer dimension.</p> Signup and view all the answers

What is the purpose of the roll-up operation in OLAP cube analysis?

<p>The roll-up operation involves summarizing the data along a dimension, using an aggregate function or a set of formulas.</p> Signup and view all the answers

What is the display format of the result?

<p>The result is a spreadsheet-style display.</p> Signup and view all the answers

What values populate row 1?

<p>Values of X populate row 1.</p> Signup and view all the answers

What values populate column A?

<p>Values of Y populate column A.</p> Signup and view all the answers

What is an OLAP cube?

<p>An OLAP cube is a multi-dimensional array of data used for online analytical processing (OLAP). It is a computer-based technique of analyzing data to look for insights.</p> Signup and view all the answers

What is the difference between a cube and a hypercube?

<p>A cube is a multi-dimensional dataset, while a hypercube refers to a dataset with more than three dimensions.</p> Signup and view all the answers

What is a slice in the context of an OLAP cube?

<p>A slice is a subset of the data generated by selecting a specific value for one dimension and displaying only the data associated with that value.</p> Signup and view all the answers

What is the purpose of the "slice" operation in OLAP cube analysis?

<p>The purpose of the &quot;slice&quot; operation is to pick a rectangular subset of a cube by choosing a single value for one of its dimensions, creating a new cube with one fewer dimension.</p> Signup and view all the answers

What is the purpose of the "dice" operation in OLAP cube analysis?

<p>The purpose of the &quot;dice&quot; operation is to produce a subcube by allowing the analyst to pick specific values of multiple dimensions.</p> Signup and view all the answers

What is the purpose of the "drill down/up" operation in OLAP cube analysis?

<p>The purpose of the &quot;drill down/up&quot; operation is to allow the user to navigate among levels of data ranging from the most summarized (up) to the most detailed (down).</p> Signup and view all the answers

What is the purpose of the "roll-up" operation in OLAP cube analysis?

<p>The purpose of the &quot;roll-up&quot; operation is to involve summarizing the data along a dimension, typically using an aggregate function or a set of formulas.</p> Signup and view all the answers

What is the display format of the result?

<p>The result is a spreadsheet-style display.</p> Signup and view all the answers

What values populate row 1?

<p>Values of X populate row $1.</p> Signup and view all the answers

What values populate column A?

<p>Values of Y populate column $A.</p> Signup and view all the answers

What is the purpose of OLAP?

<p>The purpose of OLAP is to analyze data and look for insights.</p> Signup and view all the answers

What is a cube in the context of OLAP?

<p>A cube is a multi-dimensional dataset that represents the data's dimensions.</p> Signup and view all the answers

How are measures and dimensions represented in an OLAP cube?

<p>Measures are represented as numbers in each cell of the cube, while dimensions are derived from dimension tables.</p> Signup and view all the answers

What is the purpose of the "drill down" operation in OLAP cube analysis?

<p>The purpose of the &quot;drill down&quot; operation is to allow the user to navigate among levels of data ranging from the most summarized to the most detailed.</p> Signup and view all the answers

What is the purpose of the "pivot" operation in OLAP cube analysis?

<p>The purpose of the &quot;pivot&quot; operation is to allow an analyst to rotate the cube in space to see its various faces.</p> Signup and view all the answers

What is the mathematical definition of an OLAP cube?

<p>In database theory, an OLAP cube is an abstract representation of a projection of an RDBMS relation. Given a relation of order N, consider a projection that subtends X, Y, and Z as the key and W as the residual attribute.</p> Signup and view all the answers

What are the common operations in OLAP cube analysis?

<p>The common operations in OLAP cube analysis include slice and dice, drill down, roll up, and pivot.</p> Signup and view all the answers

What is the purpose of using a spreadsheet-style display in OLAP cube analysis?

<p>to display values of g : ( X, Y ) → W at intersections of X-labeled columns and Y-labeled rows</p> Signup and view all the answers

What is the role of values of X in the spreadsheet-style display?

<p>to populate the row $1</p> Signup and view all the answers

What is the role of values of Y in the spreadsheet-style display?

<p>to populate the column $A</p> Signup and view all the answers

What is the purpose of OLAP?

<p>OLAP is a technique used for analyzing data to look for insights.</p> Signup and view all the answers

What is a cube in the context of OLAP?

<p>A cube is a multi-dimensional dataset that can be considered a multi-dimensional generalization of a spreadsheet.</p> Signup and view all the answers

What are measures and dimensions in an OLAP cube?

<p>Measures represent some measure of the business, such as sales or profits, while dimensions represent the different aspects or categories by which the data is summarized, such as product or time. Measures are derived from the records in the fact table and dimensions are derived from the dimension tables.</p> Signup and view all the answers

What are the four common operations in OLAP cube analysis?

<p>The four common operations in OLAP cube analysis are slice and dice, drill down, roll up, and pivot.</p> Signup and view all the answers

What is the purpose of the "slice" operation in OLAP cube analysis?

<p>The purpose of the slice operation in OLAP cube analysis is to pick a rectangular subset of a cube by choosing a single value for one of its dimensions, creating a new cube with one fewer dimension.</p> Signup and view all the answers

What is the purpose of the "dice" operation in OLAP cube analysis?

<p>The purpose of the dice operation in OLAP cube analysis is to produce a subcube by allowing the analyst to pick specific values of multiple dimensions.</p> Signup and view all the answers

What is the purpose of the "drill down" operation in OLAP cube analysis?

<p>The purpose of the drill down operation in OLAP cube analysis is to allow the user to navigate among levels of data ranging from the most summarized to the most detailed.</p> Signup and view all the answers

What is the purpose of the "roll up" operation in OLAP cube analysis?

<p>The purpose of the roll up operation in OLAP cube analysis is to involve summarizing the data along a dimension.</p> Signup and view all the answers

What is the star schema?

<p>The star schema is the simplest style of data mart schema and is widely used in data warehouses and dimensional data marts.</p> Signup and view all the answers

What are the components of the star schema?

<p>The star schema consists of one or more fact tables referencing any number of dimension tables.</p> Signup and view all the answers

What are the advantages of using the star schema?

<p>The star schema is more effective for handling simpler queries and provides a clear and intuitive structure for organizing data in a data warehouse.</p> Signup and view all the answers

What are the three types of fact tables mentioned in the text?

<p>Transaction, snapshot, accumulating snapshot</p> Signup and view all the answers

What are the benefits of star-schema denormalization?

<p>Simpler queries, simplified business reporting logic, query performance gains, fast aggregations, feeding cubes</p> Signup and view all the answers

What are some examples of dimension tables mentioned in the text?

<p>Time, geography, product, employee, range</p> Signup and view all the answers

What is the purpose of a surrogate key in a fact table?

<p>To ensure each row can be uniquely identified</p> Signup and view all the answers

What is the main difference between star schema and snowflake schema?

<p>The main difference is that the dimension table of the snowflake schema is maintained in the normalized form to reduce redundancy.</p> Signup and view all the answers

What are the advantages of using a snowflake schema?

<p>The advantages include easy maintenance and storage space savings. However, it may result in slower query response times and higher resource usage.</p> Signup and view all the answers

What factors should be considered when deciding between a snowflake schema and a star schema?

<p>The decision should consider query performance, schema complexity, and data integrity requirements.</p> Signup and view all the answers

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