What is junk dimension?

A junk dimension is a collection of random transcational codes flags and text attributes that are unrelated to any particular dimension.The junk dimension is simply a structure that provides the convienent place to store the junk dimension.

Operational Data Store Vs Data warehouse

Operational Data Store(ODS)	Data warehouse
ODS is an Online integration of data	Typically it won't provide online Information.  It provides offline  data.
ODS is used, when a system's data is required to access from some other systems immediately. Ex: records updated from various section, data is lying in different DB, of Hospital is required while billing or some other activities	It is used while making decisions from past and present data(bit old, may be data taken from hours or days back)
ODS is centralized repository of data for online operational use	This is Non-Operational use

What is Data warehouse?

Data warehouse is repository of data, which are collected from many sources like transactional database or old backup data, etc., and then filtered, cleansed, transformed the data for the purpose of analyzing, decision making and reporting.

Types Of Dimensions:

Dimensions are classified as followings:


1. Slowly Changing Dimensions or SCD (Type0,Type1,Type2,Type3,Type4,Type6)
2. Slowly Growing Dimensions or SGD (Type1,Type2,Type3 from SCD)


And Other Types are...


1. Conformed Dimension
2. Junk Dimension
3. Degenerated Dimension
4. Role Playing Dimension

Conceptual Data Model or Conceptual Data Schema:-

Conceptual Data Model Identifies the highest level of relationship between important entities of Data Model. It contains only important entities, no attribute, and no key specification. It contains only entity name and entity relationship as shown below

Degenerate Dimension (DD)

It is a dimension which is derived from fact table. DD doesn’t have separate dimension table. It is mostly used when we planned use transactional level information on the fact table. The main purpose of DD is to provide the info directly without referring other table.

Primary key of a fact table is subset of table's foreign key. In some cases, we do not need the foreign key in the fact guarantee the uniqueness, in that scenario, DD plays the role.


Dimension keys without corresponding dimension tables is known as Degenerated Dimensions