# Thread: Basic OLAP require !!

1. Registered User
Join Date
Dec 2003
Location
Delhi INDIA
Posts
58

## Unanswered: Basic OLAP require !!

Hi Champs!!

I am totally new in OLAP and want know more prior to start....pls tell me know the difference between these..

Star schema/ snow flake/ parent-child/ virtual dimension/ mining model

-Deepak Kumar.

2. Registered User
Join Date
Aug 2004
Posts
28

## Regarding various OLAP attributes concepts

Cubes
Cube consist of dimensions on ehich to analyse the data.

1>Regular Cube
A regular cube is based on tables in the databases specified in
the data sources of the cube's partitions

2>Virtual Cube
created with one or more regular cubes.
A virtual cube is a combination of multiple cubes in one logical
cube, somewhat like a relational database view that combines other
views and tables.Thus it contains measures from the related cubes.

A linked cube is based on another cube that is defined and stored
on another Analysis server. To end users, linked cubes appear and
function like regular cubes. By using linked cubes, you can create,
store, and maintain a cube on one Analysis server while the cube is
also available as linked cubes on multiple Analysis servers

-----------------------------------------------------------------------
**Dimension
1>Regular Dimension
every cube must has atleast one dimension.It is the default dimension.
dimensions have associated aggregation data in the cubes in which they
are used. A regular dimension contains a number of levels equal to the
number of columns selected during its definition

2>Virtual Dimension
Based on other dimensions.
A virtual dimension is a logical dimension based on the columns from
a physical dimension

3>Parent Child Dimension
A parent-child dimension is based on two dimension table columns that
together define the lineage relationships among the members of the
dimension. One column, called the member key column, identifies each
member; the other column, called the parent key column, identifies the
parent of each member. This information is used to create parent-child
links, which are then combined into a single member hierarchy that
represents a single meta data level.

For example, in the Employee table, the column that identifies each
member is Employee_Number. The column that identifies the parent of
each member is Manager_Employee_Number
-----------------------------------------------------------------------
**Mining Model
A mining model enables you to analyze your data for patterns and to make
predictions based on the patterns. You can create a mining model from a
relational schema or a cube, and you can store output from the model in
a tabular column, a cube dimension, or a mining model diagram.

------------------------------------------------------------------------

**Star Schema
Star Schema: A single dimension table

Select to create a regular dimension based on a single dimension table.
The depth of the dimension depends on the number of levels you select
in a later step. Each level is derived from a column.
When the dimension is added to a cube, the dimension table joins
to the fact table. If each of the cube's dimensions is based on a
single table, the cube has a star schema.

**Snowflake Schema: Multiple, related dimension tables

Select to create a regular dimension based on multiple, joined dimension
tables. The depth of the dimension depends on the number of levels you
select in a later step. Each level is derived from a column.

When the dimension is added to a cube, only one of its dimension
tables joins to the fact table. Therefore, the cube has a snowflake schema.

Regards
Praveen Kumar Pandey

CoVisible Soltuions

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