Answer / arasu

example for junk dimension:

consider a trade company which consists of fact about trading that take places in a share trading firm.in these there may be some facts like mode of trade(which indicates whether the user is trading through phone or online)which will be not related to any of the dimensions such as account,date,indices,amount of share etc.
so these unrelated facts are removed from the fact table and stored as a separate dimension as a junk dimension which will be useful to provide extra information

Answer / manoj

When developing a dimensional model, we often encounter miscellaneous flags and indicators. These flags do not logically belong to the core dimension tables.

A junk dimension is grouping of low cardinality flags and indicators. This junk dimension helps in avoiding cluttered design of data warehouse. Provides an easy way to access the dimensions from a single point of entry and improves the performance of sql queries.

Example: For example, assume that there are two dimension tables (gender and marital status). The data of these two tables are shown below:

Code:
Table: Gender
Id Gender_status
----------------
1 Male
2 Female

Table: Marital Status
Id Marital_Status
----------------
1 Single
2 Married
Here both the dimensions have low cardinality flags. This will cause maintenance of two tables and decrease performance of sql queries.

We can combine these two dimensions into a single table by cross joining and can maintain a single dimension table. The result of cross join is shown below:

Code:
id gender mrg_status
--------------------
1 Male Single
2 Male Married
3 Female Single
4 Female Married

This new dimension table is called a junk dimension. This will improve the manageability and improves the sql queries performance.

Answer / palzkumar

It’s simply a structure that provides a convenient place to
store the junk attributes.

Answer / suresh...

The dimension which will contain data/flags information is
called junk dimension

Answer / madhu

any yes or no like status is an example for junk dimension

Answer / sag

un wanted data which is not useful fo report generating
purpose tht data will be placed in the particular table that
table is known as junk dimension

Answer / banjwolf

A junk dimension is a table containing all known or given
combinations of two or more other dimensions. It is then
used as a lookup from a fact table to find the combination
of dimensions that relate to that fact. The purpose is to
declutter and reduce the width of the fact table.
An example might be a [SalesFact] table which references a
junk dimension [SalesExtentionDIM] containing values/SKs
for dimensions of [OnSaleYN] , [SaleCodeSK] , [ColourSK] ,
[baggedYN]

Answer / gopal

Junk Dimension are may be or may not be used
Ex-Gender M/F
student attendance.-yes/No

Answer / srinivas reddy

A Dimension with the type of descriptive information like flog,button or not used describe the key performance indicators known as facts is called as junk dimension

ex: product description,phone,fax, address ,etc..

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