Data Warehouse Concepts

Types of tables in Data warehouse:

1. Dimensions
2. Facts

Dimensions: These are attributes about facts.  Dimensions stores textural description about the business.

Facts:It stores business m measurements. Facts are actual  transactions or values being analyzed.  They contain composite primary key where each each attribute of primary key isa foreign key to the dimension table.

Fact table consists of keys and measures.

Types of facts:

1. Additive facts:
Business  measurements in a fact table that can be summed up in the fact table.

2. Semi additive facts
Business  measurements in a fact table that can be summed up Through only some dimension keys in the fact table.

3. Non Additive facts
Business  measurements in a fact table that can be summed up across any  dimension keys in the fact table

4. Cumulative fact table: It describes what was happend over a period of time.  This fact table consists of additive facts.

5. Snapshot fact table: It describes the state of things in a particular instance of time. This consists of semi additive and non additive facts.

Types of Dimensions:

1. Confirmed Dimension:

Dimensions that is shared across multiple facts or Dimension that is directly shared to join more fact tables.
Shrunken Dimensions: dimension that is subset to another dimensions or dimensions that is not directly linked to the fact table.

2. Junk dimensions:

Dimension that is organized based on low cordinality indicator of flags. Like male or female , payment mode cash or card.

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