Thursday, October 16, 2014

data cube in datawarehouse

Data cube

Data cube help us to represent the data in multiple dimensions. The data cube is defined by dimensions and facts. The dimensions are the entities with respect to which an enterprise keep the records.

Illustration of Data cube

Suppose a company wants to keep track of sales records with help of sales data warehouse with respect to time, item, branch and location. These dimensions allow to keep track of monthly sales and at which branch the items were sold.There is a table associated with each dimension. This table is known as dimension table. This dimension table further describes the dimensions. For example "item" dimension table may have attributes such as item_name, item_type and item_brand.
The following table represents 2-D view of Sales Data for a company with respect to time,item and location dimensions.
 But here in this 2-D table we have records with respect to time and item only. The sales for New Delhi are shown with respect to time and item dimensions according to type of item sold. If we want to view the sales data with one new dimension say the location dimension. The 3-D view of the sales data with respect to time, item, and location is shown in the table below:
 The above 3-D table can be represented as 3-D data cube as shown in the following figure:

Data mart

Data mart contains the subset of organisation-wide data. This subset of data is valuable to specific group of an organisation. in other words we can say that data mart contains only that data which is specific to a particular group. For example the marketing data mart may contain only data related to item, customers and sales. The data mart are confined to subjects.

Points to remember about data marts:

  • window based or Unix/Linux based servers are used to implement data marts. They are implemented on low cost server.
  • The implementation cycle of data mart is measured in short period of time i.e. in weeks rather than months or years.
  • The life cycle of a data mart may be complex in long run if it's planning and design are not organisation-wide.
    Data mart are small in size.
  • Data mart are customized by department.
  • The source of data mart is departmentally structured data warehouse.
  • Data mart are flexible.
Graphical Representation of data mart.

Virtual Warehouse

The view over a operational data warehouse is known as virtual warehouse. It is easy to built the virtual warehouse. Building the virtual warehouse requires excess capacity on operational database servers.

1 comment:

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