Schemas and its types :

Schema:

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

STAR 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:

Integrated schema:

For indepth understanding Cognos Training click on

• Cognos Tutorials
• Introduction to IBM COGNOS
• Dimensions & OLAP Types in Cognos
• Reporting Studio in IBM Cognos
• Fitters and its types in Cognos