Junk,Degenerate,Confirmed,Slowly changing dimension

Types of Dimensions

Confirmed Dimension

If the dimension is shared by multiple fact tables then the dimension is called as Confirmed Dimension.

Degenerate Dimension

It is an attribute in the fact table and used to satisfy the latest requirements from the customer

Ex: Avg No of goods sold per order= Sales Qty/OrderNo

Junk Dimension

The Dimension which Contains textual codes(Abbrevations) and flag variables is called Junk Dimension

Ex: Textual Codes - IND,USD,AUD Flag Variables - Yes/No Male/Female True/False 1/0

Large Dimension

If the dimension contains more number of columns(>100) or more number of rows(>2million), then it is called as large or monster dimension.

Mini Dimension

If the dimension contains less number of columns(<5) and less number of rows(<1000) then it is called as mini dimension

Slowing Changing Dimension(SCD)

The dimension which changes w.r.t number of rows or number of columns over a period of time, is called as slowly changing dimension

SCD are of 3 Types

Type1 - It maintains latest data only

Type2 - It maintains complete data about all transactions

Type3 - It maintains current values along with immediate previous values

Example

PNo	PName	Cost
101	Dove	15
102	Olay	20

Type II

PNo	PName	PCost
101	Dove	10
102	Olay	20
101	Dove	15

Type III

PNo	PName	Prev Cost	Present Cost
101	Dove	10	15
102	Olay	-	20

Static Dimension

If the dimension is loaded with data only once in a project life cycle time and will never change then it is called as static dimension

Example

Country - India,Pakistan,Srilanka

Currencies - USD,INR,AUD

Aggregate Dimension

The dimension which is loaded at base level and is possible to calculate aggregate functions like sum(),avg(),min() etc is called as aggregate dimension

Multi valued Dimension

If the dimension attributes contains many to many relationship within the data then the dimension is called as multi valued dimension

Types of Fact Tables

Snapshot Fact Table

Cumulative Fact Table

Factless Fact Table

Snapshot Fact Table

It contains information at a specific point of time

Ex: Sales @ 01-01-2014

Cumulative Fact Table

It contains information about a period

Ex: Sale From 01-01-2014 to 31-01-2014

Factless Fact Table

The fact table which doesn't contain any fact information is called as fact-less fact table

Ex: To track the attendance of a student, To check the product availability in a store, To check the flight availability in the airport