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Explain degenerated dimension in detail.

Asked by: Interview Candidate | Asked on: Aug 23rd, 2006
Showing Answers 1 - 9 of 9 Answers
mamatha

Answered On : Sep 1st, 2006

hi sharat

      degenerated dimension is a dimension which is not having any source in oltp

     it is generated at the time of transaction

    like invoice no this is generated when the invoice is raised

    it is not used in linking and it is also not a fkey

    but we can reffer these degenerated dimensions as a primary key of the fact table

  
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Sahitya Bindu

Answered On : Sep 12th, 2006

A Degenerate dimension is a Dimension which has only a single attribute.

This dimension is typically represented as a single field in a fact table.

The data items thar are not facts and data items that do not fit into the existing dimensions are termed as Degenerate Dimensions.

Degenerate Dimensions are the fastest way to group similar transactions.

Degenerate Dimensions are used when fact tables represent transactional data.

They can be used as primary key for the fact table but they cannot act as foreign keys.

  
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mallik

Answered On : Sep 15th, 2006

The degenerate Dimension are keyes of a fact table which do not the corresponding dimesion table.

  
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rajarajana

Answered On : Sep 15th, 2006

View all answers by rajarajana

When the cardinality of column value is high, instead of maintaining a separate dimension and having the overhead of making a join with fact table, degenerated dimensions can be build.

For example, in sales fact table, Invoice number is a degenerated dimension. Since Invoice Number is not tied up to an order header table, hence there is no need for invoice number to join a dimensional table; hence it is referred as degenerate dimension.

  
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sithu

Answered On : Mar 24th, 2007

View all answers by sithu

A Degenerate dimension is a Dimension which has only a single attribute.
This dimension is typically represented as a single field in a fact table.
Degenerate Dimensions are the fastest way to group similar transactions.
Degenerate Dimensions are used when fact tables represent transactional data.
They can be used as primary key for the fact table but they cannot act as foreign keys.
Cheers, Sithu
sithusithu@hotmail.com

  
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As The name interprets , Its not a Dimension. But rather can be Quoted as a primary key of the fact, usually a transational Fact like Premium, Money etc. It holds apart from the primary keys of the dimensions as foreign key in the fact.
This key is not a foreign key to any other Dim rather belongs solely as a primary key to the Fact. But rather can be used with other transactional Facts, with there own DD key.
I hope i answer in a better way.

  
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mri_sonam

Answered On : Dec 18th, 2008

View all answers by mri_sonam

Degenerate dimension: A column of the key section of the fact table that does not have the associated dimension table but used for reporting and analysis, such column is called degenerate dimension or line item dimension.For ex, we have a fact table with customer_id, product_id, branch_id, employee_id, bill_no, date in key section and price, quantity, amount in measure section. In this fact table, bill_no from key section is a single value, it has no associated dimension table. Instead of cteating a seperate dimension table for that single value, we can
include it in fact table to improve performance.SO here the column, bill_no is a degenerate dimension or line item dimension.

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SarthakB

Answered On : Apr 9th, 2009

View all answers by SarthakB

Degenerated Dimension is achieved through a gradual modeling approach
following Dimensional Modeling standards. Let's take example of a Star Schema
representing Sales Invoices. The FACT would have the "Invoiced Amount" as
primary measure. Now when we look at the source of the Invoice, it is the body
if the Paper Invoice that gives us the following particulars about each Invoice:


Invoice Date

Customer ID

Products within the Invoice

Reference to Order Number(s)

Invoice Number

Invoice Line Numbers (which are multiple lines in single Invoice)

Invoice Line Amount

Invoice Total Amount


When we model the above following Dimensional Modeling standards, we get
following distinct Dimensions:


Calendar Dimension - representing the Invoice Date

Customer Dimension - representing Customer ID

Product Dimension - representing Products within the Invoice

Order Dimension - representing Orders

Invoice Dimension representing Invoice Number & Invoice Line Numbers


Question comes - what attributes would be left to be part of the INVOICE
DIMENSION, if at all we decide to have one! Only candidate attributes are
Invoice Number and Invoice Line Numbers. But, this is at the granularity of the
FACT, which stores references to all above said Dimensions as well as the
measures i.e. Invoice Line Amount, Invoice Total Amount (Derived by
aggregation).


It is at this situation, we may decide to degenerate the attributes Invoice
Number & Invoice Line Number into the Fact and avoid having a distinct entity to
represent Invoice Number / Line Numbers as a Dimension. What we achieve by this:


1. avoiding a huge join as both Fact and this Dimension would have the same
granularity,

2. still able to query with Invoice Number as the entry point


So, when such a scenario appears, we make the left out attributes (i.e.
Invoice Number & Invoice Line Number in our case) part of the Fact and part of
the Primary Key in the Fact. This is why and how we model Degenerated
Dimensions.

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Veera reddy

Answered On : Feb 20th, 2012

If a table contains the values, which are neither dimension nor measures is called degenerate dimensions.Ex : invoice id, empno

  
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