Data With Gaurav

Types of dimensions: ·          Role playing Dimension ·          Conformed Dimension ·          Junk Dimension ·          Degenerate Dimension ·          Slowly Changing Dimension ·          Rapidly changing Dimension ·          Inferred Dimension 1. Role playing Dimension: When dimension table is having  more than FK relationship with Fact table  is called Role playing dimension. Ex: SaleDateKey and DeliveryDateKey      2. Conformed Dimension: ·          A conformed dimension relates to multiple fact tables within the same DWH. ·          DimDate  is a common conformed dimension...

  SCHEMAS:   Star Schema: -       Star Schema means Dimension Tables are directly linked to the Fact Table. Snow Flake Schema: -       Dimension Tables are indirectly linked to the Fact Table OR -       Dimension table is linking to another dimension table .       Star Schema   Snow Flake Schema 1 Has redundant data and hence tough to maintain/change 1 No redundancy and hence more easy to maintain/change 2 Less complex queries and hence easy to understand 2 More complex queries and hence less easy to understand 3 Less foreign keys so faster execution time of cube. 3 More foreign keys so take more execution of cube 4 Has De-Normalized Tables 4 Has Normalized Tabl...

OLTP (Online Transaction Processing):   ·          Fresh Data ·          Read (20%) and write (80%) ·          Small Data (500GB) ·          Normalized Data ·          More Users ·          Less Indexes   OLAP/DWH (Online Analytical Processing):   ·          Historical Data ·          Read only Data ·          Large Data (TB) ·          De-Normalized Data ·          Less Users ·          More Indexes   SNO OLTP (Operational Data) OLAP ...

In shot what is DWH (Data warehouse)? A DWH is a Large Database which consists of Dimension and Fact tables. Or Collection of DataMart is called as a DWH. Father of Data Warehouse: Dr. William H. Inmon Dr. Ralph Kimball -Introduced Dimension Modelling to design DWH in 1990. What is Data Warehouse? As per Dr. William Inmon, Data Warehouse is a -       Subject Oriented (Loans, Mutual Funds etc.) -       Integrated (Get data from various sources) -       Time Variant (Different time period data)   ·          *Datamart is Subject Oriented ·          *DWH is a collection of Datamart ·          *DWH is a superset of Datamart ·          *Datamart is also another database. Top-down Approach: (DWH->Datamarts)   ...