Schemas and its types :


A schema is nothing but a collection of objects

  • Designing a dWH is nothing but designing the schema
  • A data ware house tables are contain dimensional tables and fact tables
  • Database models follows dimensional modeling to design dWH schema
  • Dimensional modeling is a process of creating dimensional tables and fact tables with proper relation

Types of schemas:

  1. Star schema
  2. Snow flake schema
  3. Galaxy schema (or)integrated schema (or) constellation schema


A star schema design is a data base design where the centrally located table is called fact table with surrounded by number of dimensional tables

  • Since the database design looks like star, it is called star schema

Format of star schema:


Dimensional tables:

  • A dimensional table contains detail information (or) descriptive information
  • Dimensions are used to describe the facts.

Fact table: 

  • A fact table contains all the key columns (PK, FK) and measures of the particular business organizations.
  • Measures are also called as facts (or) KPI’s (key performance indications)
  • fact should be a numeric but every numeric near not be a fact.

Sales schema


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Snow flake schema:


Difference between the schema and snow flake schema:

Star schemaSnow flake schema
It is de normalizedRetrieval up data is faster

redundancy is there

 it is normalizedRetrieval up data is slower due to more number of icons

redundancy can be reduced

Integrated schema:


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