Reply to the following posts(no criticism):1.Data Warehousing and Dimensional ModelingCOLLAPSE Data warehouse: has data on multiple subjects has multiple data sources from multiple areas of data...

Data warehouse:

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  has data on multiple subjects

  
  


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  has multiple data sources from multiple areas of data

  
  


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  occupies large memory

  
  

Data mart:

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  smaller version of a data warehouse

  
  


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  has data on particular subject

  
  


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  quicker to build data mart than a data warehouse

  
  


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  draws data from a limited number of sources

  
  


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  occupies limited memory

  
  

Data warehouses are used as a central location where consolidated data from multiple locations can be stored. Data stored in the data warehouse are used for analyzing, reporting, and decision making.

Dimensional Modeling is a design technique for databases intended to support end-user queries in a data warehouse. Data is denormalized and descriptive data and quantity data are split in dimensional modeling. The resulting model reflects questions the business would ask, as opposed to functions managed by the underlying system.

Dimensions describe business events like the sale of a product. It is data that can be considered descriptive and non-quantitative. Users usually sort, group, and filter based on dimensions.

Facts are a measurable metric which is described by the dimensions which are represented in numerical forms.

In a Star Schema, dimensions relate to the fact table only. The dimensions are denormalized, and the dimension keys are generated by the data warehouse load processes and not the source systems.In a Snowflake Schema, dimensions can relate to other dimensions. This may cause some performance and usability issues because of the relations.

1. List the differences data warehouses anddatamarts?Briefly discuss the reasons Data Warehouses are used?


2. Explain the concept "Dimensional Modeling". Differentiate between dimensions vs facts; star vs snowflakeschemas

1-Datamartsare sub category of the full data warehouse. The data warehouse is used because it stores large and varied amounts ofdatafor you torun queries on.

2-Dimensional Models are created to make big picture models to display and analyze data. A dimensional table has a primary key and a set of attributes. A fact table has a set of foreign keys that define it and is used as a transactional key to attach an order or transaction to other primary key tables. Star and Snowflakeschemasbothhave one fact table surrounded by multiple dimensional tables, in a startableall of the dimensional tables aredenormalizedwhilein a snowflake schema they would undergo normalization